Agnimandur's blog

April Fools Day Contest 2022
By Agnimandur, history, 3 years ago, In English

With Nickolas not writing a contest this year, magnus.hegdahl and I have decided to take up this sacred duty :). We would like to invite everyone on Codeforces to the April Fools Day Contest 2022. Special thanks to BucketPotato for volunteering to test this contest!

The 10th April Fools Day Contest will take place on Apr/01/2022 17:35 (Moscow time). This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.

In this round you'll be given several weird problems and 2 hours to solve them. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated. You can submit solutions in any language allowed by Codeforces, unless the problem says otherwise. To get an idea of what the contest will look like, you can check out the contests of the past years: 2012, 2013, 2014, 2016, 2017, 2018, 2019, 2020, 2021.

Good luck, and have fun!

UPD: There will be 8 problems. There will be only be an interactive problem if the Collatz Conjecture is true...

UPD: Thanks to everyone who participated! I hoped you enjoyed thinking over the problemset. The editorial is available, complete with solution code and hints. Special congratulations to the winners.

Rank Username Score
1 Lotus 7 (330)
2 DeepOcean 7 (339)
3 xyf007 7 (341)
4 Tyyyyyy 7 (345)
5 Flamire 7 (345)
  • Vote: I like it
  • +538
  • Vote: I do not like it

Comments Comments (162)
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3 years ago, # |
  Vote: I like it +187 Vote: I do not like it

as a tester, give me contribution.

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3 years ago, # |
← Rev. 2   Vote: I like it +47 Vote: I do not like it

Guess there will be 'Is it rated? — 3'

upd: OK now it really appears in Problem D!!!

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3 years ago, # |
  Vote: I like it +102 Vote: I do not like it

UPDATE: The contest will be hosted on the Codeforces contest page! Everyone can register here.

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3 years ago, # |
  Vote: I like it +25 Vote: I do not like it

Is it rated?

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3 years ago, # |
  Vote: I like it +19 Vote: I do not like it

Isitrated?

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3 years ago, # |
← Rev. 3   Vote: I like it -95 Vote: I do not like it

[deleted]

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3 years ago, # |
  Vote: I like it +19 Vote: I do not like it

This will be my first April fool Day contest :) Really excited

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3 years ago, # |
  Vote: I like it +85 Vote: I do not like it

There will be only be an interactive problem if the Collatz Conjecture is true.

WHAT THE HECK

Spoiler
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3 years ago, # |
← Rev. 2   Vote: I like it +64 Vote: I do not like it

Sorry i'm not familiar with c++, can anyone tell me what this code will output?

#include<bits/stdc++.h>
using namespace std;

int main()
{
	int p[15]={73,115,32,105,116,32,114,97,116,101,100,63};
	for(int i=0;i<12;i++) printf("%c",p[i]);

	return 0;
}
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    3 years ago, # ^ |
      Vote: I like it +8 Vote: I do not like it
    mutsuki orz
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    3 years ago, # ^ |
      Vote: I like it +73 Vote: I do not like it

    Or this:

    #include<bits/stdc++.h>
using namespace std;

int f(int x) {
    return 5*5179*68111 + (3*61576747*x)/2.0 - (17137*25819*x*x)/2.0;
}
int main()
{
	int p[]={f(0),f(1),f(2),0};
	printf("%s",&p);

	return 0;
}
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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    code art

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Don't forget to register for the contest before it starts, good luck, and have fun!

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3 years ago, # |
  Vote: I like it +44 Vote: I do not like it

don't forget to check the unusual timing

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3 years ago, # |
← Rev. 3   Vote: I like it 0 Vote: I do not like it

Hallo Codeforces.I'm Tobi and this is my first April Fool's contest. And I don't know if it has a rating or not? Please give me your answer!And have a fun at the April Fool's contest.Good luck :).

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3 years ago, # |
  Vote: I like it -37 Vote: I do not like it

My first unrated April Fools contest as an expert :p

Spoiler
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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    haha, this is so fun!!!! :DDDDDDDDDDDDDDDDD I cannot stop laughing :DDDDDDDDD please eat your cat

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Looking forward to it :)

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3 years ago, # |
← Rev. 2   Vote: I like it -6 Vote: I do not like it

I'm a boy, it's a joke!

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3 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

tonight, who can carry me?

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

The Collatz Conjecture is true... )))

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3 years ago, # |
  Vote: I like it +26 Vote: I do not like it

Imagine the contest being unrated a April fool Joke itself

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3 years ago, # |
  Vote: I like it +26 Vote: I do not like it

Is it OK to participate in a team? It would be more enjoyable.

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3 years ago, # |
  Vote: I like it +1 Vote: I do not like it

This will be my first April Fool Day contest. Really (EXCITED).٩ (◕‿◕｡) ۶

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Announcement: This competition will be rated! just go all out!

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3 years ago, # |
  Vote: I like it +1 Vote: I do not like it

What is Collatz Conjecture?

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3 years ago, # |
  Vote: I like it +1 Vote: I do not like it

There will be only be an interactive problem if the Collatz Conjecture is true...

Is there a typo or does the first be have a meaning?

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    3 years ago, # ^ |
      Vote: I like it +2 Vote: I do not like it

    There's probably a hint for the hardest problem, hidden somewhere in this sentence.

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3 years ago, # |
← Rev. 2   Vote: I like it +8 Vote: I do not like it

just imagine there is no contest :(

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

"The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated." Is this also a joke?

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3 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Is it a rated one?

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3 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Is there any time penalty for wrong submission ? If answer is yes , then how much ?

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

contset is rated or unrated for div 2

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3 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Where can I see the question form so I can code it?

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3 years ago, # |
← Rev. 2   Vote: I like it +3 Vote: I do not like it

codeforce is giving wrong output on code whereas rest other compilers giving right answer

1st image

This screenshot is of other compiler of same code(all other online compilers are also giving same output)

2nd image

Here is code can you run on your compiler check 152301548

Spoiler
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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Collatz Conjecture isn't true...

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    3 years ago, # ^ |
    ← Rev. 2   Vote: I like it -11 Vote: I do not like it

    I proved Collatz Conjecture yesterday lol UPD: really simple thing

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3 years ago, # |
  Vote: I like it +13 Vote: I do not like it

Okk I have been successfully made fool

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3 years ago, # |
  Vote: I like it +9 Vote: I do not like it

DON'T CLICK THE TUTORIAL, I regretted doing that.

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    3 years ago, # ^ |
      Vote: I like it -8 Vote: I do not like it

    my internet speed is slow, so i had time to close rickroll)

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I figured that E involves finding "minotaur" in the grid but no idea why it fails on test 6 :(

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

It's a funny round! :)

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3 years ago, # |
  Vote: I like it +9 Vote: I do not like it

Can someone tell me why does this 152408291 fail on H it compiles both on pascal and C++

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    3 years ago, # ^ |
      Vote: I like it +3 Vote: I do not like it 
    Free Pascal Compiler version 3.0.4 [2017/10/03] for x86_64                                                                                                                                                           Copyright (c) 1993-2017 by Florian Klaempfl and others                                                                                                                                                               Target OS: Linux for x86-64                                                                                                                                                                                          Compiling program.cpp                                                                                                                                                                                                program.cpp(5,5) Warning: Comment level 2 found                                                                                                                                                                      program.cpp(8,7) Fatal: Syntax error, "BEGIN" expected but "end of file" found                                                                                                                                       Fatal: Compilation aborted
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      3 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Weird, it's compiling just fine on custom invocation.

      is it because of the version difference?

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3 years ago, # |
  Vote: I like it +30 Vote: I do not like it

How on earth are you supposed to figure out that C involves finding the sum of the array?

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

In case you're getting WA on test 3 for problem D and don't know why:

Spoiler
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3 years ago, # |
  Vote: I like it +2 Vote: I do not like it

Those who got AC in Problem B and Problem D were interactively running the binary search! :)

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3 years ago, # |
  Vote: I like it +5 Vote: I do not like it

wait wtf? is it really rated?

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3 years ago, # |
  Vote: I like it +610 Vote: I do not like it

To not keep you waiting, the ratings are updated preliminarily. In a few days, I will remove cheaters and update the ratings again!

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3 years ago, # |
  Vote: I like it +12 Vote: I do not like it

H was pretty cool.

Spoiler

Did anyone come with something else?

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    3 years ago, # ^ |
      Vote: I like it +34 Vote: I do not like it

    I used the fact that const is a valid keyword in both C++ and Free Pascal. Then mixed different types of comments (* *), /* */ and // for this weird solution:

    Spoiler
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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    I did the same thing, but for some reason my code didn't work, does anyone have an idea why?152412785

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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    I tried to use the fact that you can start a C program with (*a);, which looks like the start of a pascal comment.

    Spoiler

    This compiles with gcc, but this is NOT valid C++.

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3 years ago, # |
← Rev. 2   Vote: I like it +2 Vote: I do not like it

is the +179 rating i got an april fools joke? i thought it was unrated

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3 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Why it's rated?

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3 years ago, # |
  Vote: I like it +6 Vote: I do not like it

In my opinion this April Fools contest was the funniest one than ever :) :) :)

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3 years ago, # |
← Rev. 4   Vote: I like it +75 Vote: I do not like it

Problem C: I converted "Pōja Verdon" from Unicode (the non-ASCII ō makes me think this problem has to do with Unicode) to binary using this service and got 01010000 101001101 01101010 01100001 00100000 01010110 01100101 01110010 01100100 01101111 01101110. Using the same service, I converted the binary to ASCII and got P¦µ0+2¹27·.

Then I thought the problem was about finding a prime that is divisible by $$$\mu_0 + 2^1 \times 27$$$ :')

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    3 years ago, # ^ |
    ← Rev. 2   Vote: I like it +46 Vote: I do not like it

    and then my second attempt was to realize that $$$3979$$$ (the constraint in the problem) was tourist's highest rating (and Codeforces highest ever rating). Then I thought the problem was given $$$N$$$ ratings, find something. Then I guessed the something was to print the team rating of those $$$N$$$ ratings :')

    Completely off-track :')

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      3 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      I also tried calculating the team rating; the first translation of the title I found was "their number", and seeing the constraints I thought that would just be a way of saying "their rating", which could mean "their team rating".

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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Problem B: I remembered this blog, then I web scraped the ratings of all the users and I printed the rating of the previous user in the standings :D
    152344694

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3 years ago, # |
  Vote: I like it +32 Vote: I do not like it

There will be only be an interactive problem if the Collatz Conjecture is true

There is not any interactive problem, so Collatz Conjecture is not true

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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    there was no "if and only if" :D

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      3 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      saying "There will only be an interactive problem if the Collatz Conjecture is true" is equivalent to saying "the Collatz Conjecture is not true if there are no interactive problems" because it is the original statement's contrapositive :) Contraposition

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

As we see, it is rated :D

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3 years ago, # |
← Rev. 2   Vote: I like it +43 Vote: I do not like it

Guess: at the end of the day Mike will send the "we caught you cheating" message to every participant and undo the rating changes.

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3 years ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

1 April is a very good day with very good jokes and contests)))

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3 years ago, # |
  Vote: I like it +25 Vote: I do not like it

Why is it rated????????????????????????????

blue again

it is not funny mikkie

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    3 years ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    You just had to solve Mikkie's sequence to remain pink. LOL.

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      3 years ago, # ^ |
        Vote: I like it +3 Vote: I do not like it

      but this task is too hart how can i solve it? i dont now anything about cf rating changes

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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    i think , we will be back in our prev rating.

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3 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Wait till you see the rating changes today

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3 years ago, # |
  Vote: I like it +3 Vote: I do not like it

I think is it just prank !!
We will get our older rating after some amount of time :)
So... chillleeexxx !!

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3 years ago, # |
  Vote: I like it +2 Vote: I do not like it

Thanks for your April Fools Day's joke, Codeforces! This may be my best standing forever(the 45th). Besides, Rating changing really give me a surprises(Though I know it's a joke). This kind of problems is really interesting, I solved ABCDEH. This make me very happy. Thanks!

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3 years ago, # |
  Vote: I like it +9 Vote: I do not like it

It is Unrated. But they increased our Rating.. Good way to fool Us lol

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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    they decreased my rating, could have made me specialist for few mins. Not fair.

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3 years ago, # |
← Rev. 2   Vote: I like it -75 Vote: I do not like it

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3 years ago, # |
  Vote: I like it -26 Vote: I do not like it

Don't do such stuff codeforces, what if someone has a weak heart.

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3 years ago, # |
  Vote: I like it -21 Vote: I do not like it

Thanks for making me enjoy being pupil for a day or something idk

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Just now I dropped 229 rating.....

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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    What a pity,hh.On April Fool's day, we can never think of what will happen the next second

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

Guys..it is unrated right??then why rating has been changed??

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3 years ago, # |
← Rev. 2   Vote: I like it +4 Vote: I do not like it

Rated. lol, Proved me a big fool.

prediction: the ratings will back to normal again soon.

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3 years ago, # |
  Vote: I like it +11 Vote: I do not like it

wuhu!! Expert!!! happy!!

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3 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Is it rated or being rated is an April Fool??

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

What just happened !!! Surely some sort of prank

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3 years ago, # |
  Vote: I like it +3 Vote: I do not like it

I am satisfied with my new rating so make this contest rated

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3 years ago, # |
  Vote: I like it +81 Vote: I do not like it

Sir please sir MikeMirazayanov please give me back my rating bro sir

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3 years ago, # |
  Vote: I like it +20 Vote: I do not like it

people who's rating decreased:-"NO WAYYYY MAN!"
people who's rating increased :-"OH YEAHHHH!"

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3 years ago, # |
  Vote: I like it -34 Vote: I do not like it

is there a problem with codeforces now? in the contest the site is very slow and now the contest became rated and many people loss about -200 in a joke contest?MikeMirzayanov

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

It was an unrated contest! Now, what about the rating changes -_- ...

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3 years ago, # |
  Vote: I like it -18 Vote: I do not like it

1/April is a good day to fuck the rate for people Say that the contest is unrated and make every one join for fun after that make the contest rated :(

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

изменение рейтинга останутся или завтра возвратят?

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3 years ago, # |
← Rev. 2   Vote: I like it +3 Vote: I do not like it

Despite the fact that the announcement states that it will be unrated, the rating for this round was still counted. Is this an April Fool's joke?

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

"Unrated round"

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3 years ago, # |
  Vote: I like it +4 Vote: I do not like it

It was the first time I gave such a contest, but it was interesting and I liked it very much =D

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3 years ago, # |
  Vote: I like it +1 Vote: I do not like it

in previous contest i have become specialist for the first time and now i have become again april fool for a day. Jaane ke jid na kro..

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3 years ago, # |
  Vote: I like it +3 Vote: I do not like it

Can someone explain to me why this contest is rated ? Because I read that it is unrated

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3 years ago, # |
  Vote: I like it +9 Vote: I do not like it

Commenting before I lose expert.

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3 years ago, # |
  Vote: I like it +3 Vote: I do not like it

they make us april fool my making it rated .lol

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3 years ago, # |
  Vote: I like it +89 Vote: I do not like it

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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    meanwhile i gained 179 lmao. its cool and all but some people lost their ratings. i hope this is an april fools joke

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      3 years ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      ya apparently it's a joke I'm just trolling :)

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    3 years ago, # ^ |
      Vote: I like it +11 Vote: I do not like it

    Oh wooooow

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      3 years ago, # ^ |
        Vote: I like it +28 Vote: I do not like it

      Mike Mirzayanov just smacked the S out of me

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3 years ago, # |
  Vote: I like it +4 Vote: I do not like it

Thank you very much for the free points <3:

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3 years ago, # |
← Rev. 2   Vote: I like it -8 Vote: I do not like it

Why this contest is rated. In announcement it was written unrated. Oh, it is fixed now.

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3 years ago, # |
← Rev. 3   Vote: I like it 0 Vote: I do not like it

wtf missed this contest as I thought it would be unrated

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3 years ago, # |
  Vote: I like it -15 Vote: I do not like it

I think it is a April Fool Joke that it is rated,isn't it? Our rating points didn't changed in fact,yes?

I just read the problems and solved the first problem and went to sleep! But today I found that I have lost 100 points! It is a Joke!

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3 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Very Good Contest Thank you for greating it

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

i'll never participate in April fools contest again.

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

When will the editorial be released?

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3 years ago, # |
  Vote: I like it 0 Vote: I do not like it

I am a professional, Therefore give me contribution.

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    3 years ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Hello a professional, Therefore give me contribution. I'm AR69420.

    → Reply