Hi everyone!

Codeforces Round #373 (Div. 1 + Div. 2) will take place on 23 September 2016 at 16:05 MSK. Please note that the timing is unusual.

This time tasks for you were prepared by me (Matvey Aslandukov) and my brother _XuMuk_ (Andrew Aslandukov). It is our first codeforces round and we hope you'll enjoy it. We want to say special thanks to Seyaua (Ievgen Soboliev), AlexFetisov (Alexandr Fetisov) and winger (Vladislav Isenbaev) for testing the problems, GlebsHP for his help with the contest preparation, and MikeMirzayanov for the excellent platforms Polygon and Codeforces.

Coincidentally, the date of the round falls on my birthday, so I am very happy that I can spend that day surrounded by our friendly community :)

There will be five problems and two hours to solve them. Traditionally, the scoring distribution will be announced later.

Good luck!

UPD1:

Scoring:

Div. 2 : 500 1000 1500 2250 2250

Div. 1 : 500 1250 1250 2000 2500

The problems are sorted by difficulty but as always it's recommended to read all the problems.

UPD2:

Contest complete! Thank you all for participating :)

Unfortunately, as noted Um_nik, many solutions of div.1 B task, including the author's, were incorrect. Now we are working on this problem. If we still manage to find the right solution and answers on pretests will be the same, the round may be rated. Otherwise, it will be unrated.

Thus final results significantly delayed. We apologize for the situation. If you have thought about the correct solution — write to us.

UPD3:

We made a decision to start system testing with the current solutions and tests. The question will be round either rated or not is still opened.

UPD4:

After considering different option and estimating their pros and cons, Codeforces team decided that the main factor to make a decision on whether the round should be rated or not is how much the bug affected the results.

In the second division, only two participants managed to implement the correct greedy algorithm for the original incorrect version of the problem D, thus we consider the effect of this problem on the final standing to be negligible. The contest for division two will be rated.

Things are very different for division one, as there were plenty submission to problem B and problems B and C took the most part of participants worktime during the contest. Assuming this fact we suppose that this bug affected the final results a lot and there is no way to consider its influence on each particular participant. As a result, the contest for division one will be unrated.

The only thing left to do is to apologize to the participants. We will do our best to avoid such situations in the future.

UPD5:

Congratulations to the winners!

Div.1:

1. enot110
2. Egor
3. KrK
4. UsedToBe
5. IvL

Div.2:

1. Adenium_Rose_Of_Desert
2. GS_ZJ_137
3. haqkux201
4. MemoryLimitExceeded
5. immortalCO

Editorial is ready!

I know what is the problem

Where we are going we need all the courage we can get

When I first read the comment that our shiny new gcc 6.2 C++14 compiler has slow printf and scanf I immediately knew what I would do the next weekend. The new MinGW switched to custom implementation and I didn't need anything else to tell what the problem is. Of course, their format string parsing is too slow, they copy data around countless times, no file buffering is used and they have enough levels of indirection to make finding the real code feeling like a treasure hunt. What else could be the problem after all?

Keeping this thoughts in mind I patiently waited for a weekend. When I finally opened MinGW source and searched for printf function, I was pleasantly surprised. The real implementation was only a couple hops away and soon enough I was looking at the heart of printf code. MinGW did try to conceal it a bit though by naming it mingw_pformat.c. But a ~100Kb source file was a very clear hint where all the action is. The format string parsing was straightforward and located in a single big function. Everything was passed by pointer and there were hardly any levels of indirection. But the data was clear — MinGW printf is twice as slow for integer numbers compared with msvcrt.dll and scanf is even worse. Increasing the file buffer size didn't help at all. Reluctantly, I had to admit that the problem is somewhere else. But what could possibly be the problem?

Welcome to 2016-2017 CT S03E03: Codeforces Trainings Season 3 Episode 3 - 2007-2008 ACM-ICPC, Central European Regional Contest 2007 (CERC 07). The training duration is 4.30 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be available as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

We are planning to start on September, 21, 2016 13:10 (UTC).

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

Good luck!

Hi, everyone!

Tomorrow, on September 18, 2016, at 12-00 the Final Round of Russian Code Cup 2016 will take place. Top 50 participants of the Elimination Round will take part in the contest and have a chance to win great prizes. The length of the Final Round this year is 2 hours, the Final Round participants will compete online. You can watch the Final Round at http://russiancodecup.ru

Meanwile we are pleased to announce that the Russian Code Cup team together with Codeforces project have prepared a small surprise to all those who didn't manage to get to the Final Round of RCC-2016. After the Final Round ends, at 14-05 Codeforces will host online-contest with RCC-2016 Final Round problems.

The contest will use ACM ICPC rules and will not be rated. Problems will be in English and in Russian. Problems were prepared for Russian Code Cup Final Round, so they are quite difficult, the contest is mostly suitable for Div1 participants. Of course, we would like to ask the Final Round participants do not use the contest for testing their upsolved solutions, please wait until the end of the online contest and use the problem archive.

So, everyone is welcome to watch the Final Round and then to take part in the online-contest! Good luck to everybody!

Hi everyone, it's me again!

Codeforces Round #372 (Div. 1 + Div. 2) will take place on 17 September 2016 at 16:35 MSK,

After my last round, this will be my second round on Codeforces. I believe you'll find the problems interesting and I hope you'll enjoy the round.

This round would not be possible without danilka.pro who improved one of the problems that made this round possible, and also helped in preparing and testing the round. Also, thanks to all the testers, IlyaLos, HellKitsune and phobos and thanks to MikeMirzayanov for the awesome Codeforces and Polygon platforms.

ZS the Coder and Chris the Baboon's trip in Udayland is over. In this round, you'll help ZS the Coder solve the problems he have randomly came up with. Do you have what it takes to solve them all?

The problems are sorted by difficulty but as always it's recommended to read all the problems.

We wish you'll have many solutions and enjoy the problems. :)

As usual, the scoring will be published right before the contest.

UPD : There will be 5 problems in both division as usual.

Scoring :

Div. 2 : 500 — 1000 — 1500 — 2000 — 2500

Div. 1 : 500 — 1000 — 1500 — 2500 — 2750

Good luck and I hope you enjoy the problems!

UPD : Contest is over. I hope you enjoyed the contest and problems :) I'm sure some of you wants to see the editorial now, so here it is while we wait for System Test to start.

UPD : System tests is over. Here're the winners :

Division 1 :

1. jqdai0815

2. matthew99

3. jerry

4. Burunduk1

5. JoeyWheeler

6. LHiC

7. SanSiroWaltz

8. dotorya

9. Arterm

10. zeliboba

Division 2 :

1. amethyst0

2. JOHNKRAM

3. huzzah

4. Vax

5. KyleChen

6. LeiQ

7. Tomer.Adar

8. creatnx

9. OrangePlus

10. Yukikaze

Congratulations to them!

Welcome to 2016-2017 CT S03E02: Codeforces Trainings Season 3 Episode 2 - 2004-2005 Open Cup, Volga Grand Prix. The training duration is 4.30 hours. It is opened for teams as well as for individual participants. After the end you may use the practice mode to complete problem solving. Also it will be availible as a virtual contest for whose of you who can't take part today. Please, do not cheat. Only fair play!

We are planning to start on September, 14, 2016 13:10 (UTC).

It is possible that the problems will be too easy for some participants, it is possible that we will add some problems.

Good luck!

Hi everybody!

Codeforces Round #371 takes place on 13 September at 19:35 MSK for the both divisions. This is our first round and we hope it won't the last one.

This round is prepared by me (Anton Tsypko) and Sonechko (Sofia Melnyk). We want to say thanks to GlebsHP (Gleb Evstropov) and Sereja (Sergey Nagin) for help with preparation of this round, MikeMirzayanov (Mike Mirzayanov) for Codeforces and Polygon systems, iSlava (Viacheslav Ocheretnyi), AllCatsAreBeautiful (Mark Mikhno), BigBag (Matvey Aslandukov), winger (Vladislav Isenbaev) and AlexFetisov (Alex Fetisov) for testing problems.

It's recommended for both divisions to read the Interactive Problems Guide before the round. Scoring distribution will be published right before the start of the contest.

Good luck!

Scoring:

Div 2: 500 — 1000 — 1000 — 2000 — 3000

Div 1: 500 — 1000 — 2000 — 2000 — 2000

Upd: Congratulations to the winners:

Div 1:

1. geniucos
2. Herzu
3. Endagorion
4. Um_nik
5. Radewoosh

Div 2:

1. fanache99
2. amethyst0
3. Gromah
4. serlis
5. Jason_zjj3

Editorial.

UPD: We are sorry that Div 1 C is very similar to this, but the contest will be rated.

In the very beginning of this post I would like to thank everyone who contributed to make this contest happen — both onsite and online versions. Thanks a lot to GlebsHP for helping to organize mirror on Codeforces.

Last year there were 4 teams that solved all the problems before contest ended so we tried to make this year's problems a bit harder. I would also like to mention that 2042 teams registered to this contest,676 managed to solve at least one problem and there is 1 teams that solved all the problems before contest ended. Congratulations to everybody!

Congratulations to tourist and VArtem for winning this competition!

Ok, so here is top 10 of Codeforces version of Bubble cup: