Hello, Codeforces!

I'd like to invite you to Codeforces Round #346 (Div. 2). It'll be held on Wednesday, March 30 at 16:05 (UTC) and as usual Div. 1 participants can join out of competition. Note that round starts in the unusual time! Also, the round itself will be unusual: there will be 7 problems for two and a half hours.

Me (IlyaLos), Edvard Davtyan (Edvard), Dan Sagunov (danilka.pro), Roman Glazov (Roms) and Vladimir Petrov (vovuh) prepared the tasks for this Round. Great thanks to Gleb Evstropov (GlebsHP) for helping us preparing the contest, to Maria Belova (Delinur) for translating the statements into English and to Mike Mirzayanov (MikeMirzayanov) for the great Polygon platform, for helping on preparing the contest and for ideas for some tasks.

The scoring distribution will be announced later. Good luck everyone!

UPD Score distribution: 500-1000-1000-1250-1500-2000-2500

UPD2 Competition completed! Thank you all! Editorial

Hello everybody!

I'm glad to announce that Round 1 of VK Cup 2016 will take place this Monday, and me (Radewoosh) and Kamil Dębowski (Errichto) are the problemsetters!

There will be an official round for teams from VK cup, but if you are not eligible to participate in it, then you can compete (alone, not in team) in one of two additional editions (one for div.1 and one for div.2), so everybody is invited to take part in the competition! Just register in your category here. All three rounds will be rated. Div.1 and Div.2 editions will look like normal CF round, but will have common problems with official edition.

If you can't register before the round, then you will be able to do it during the contest (but not for the entire duration, you can cheсk it here). Let's thank Mike for this great feature!

We want to thank GlebsHP for help in preparing the problems and MikeMirzayanov because without him we wouldn't have such a great platform as Codeforces, where we all can train and develop our passion.

You will again help Limak, your favorite bear. This time it may be harder, because evil Radewoosh will try to disturb him.

We wish you good luck and great fun! Can't wait to see you during the contest! :D

UPD Scoring will be:

For VK: 500 — 750 — 1000 — 1500 — 2000 — 3000

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

For Div.1: 500 — 1000 — 1500 — 2000 — 3000

UPD Editorial is ready.

UPD Congratulations to the winners!

In official VK:

1.Never Lucky: subscriber and tourist
2.SobolevTeam: Seyaua and sdya
3.LNU Penguins: witua and RomaWhite
4.Dandelion: Um_nik and sivukhin
5.uıɟɟnɯ ɐuɐuɐq ǝɥʇ ɟo uɹnʇǝɹ╰(º o º╰): enot110 and romanandreev

In Div.1

1.dotorya
2.kcm1700
3.JoeyWheeler
4.KrK
5.Swistakk

And in Div.2

1.osmanorhan
2.nhho
3.fudail225
5.agaga
4.alanM

Also let's thank qwerty787788 and AlexFetisov for testing problems, without them it would be much harder to prepare contest, so give them an applause!

Hello, Codeforces!

[Note the unusual (for the educational round) start time!]

Educational Codeforces Round 10 will take place after a long delay on 25 march 2016 at 16:00 MSK for the first and the second divisions. The long delay is caused by the high frequency of contests and championships on Codeforces. You can read about educational rounds here and here.

<The same as before>

The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.

If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to me.

It seems that it is harder to invent interesting simple problems (like A and B) than difficult ones. So don't be afraid to suggest interesting simple or very simple tasks.

</The same as before>

From now traditionally the problemset was totally suggested by Codeforces users. The problem А for the third time was suggested by user unprost (no hope for the short problem statement :-)). The problem B was suggested by user Smaug. The problem C is another problem from the set sent by Bayram Berdiyev bayram, Allanur Shiriyev Allanur and Bekmyrat Atayev Bekmyrat.A. Alexey Dergunov dalex suggested the problems D and E. The problem F was suggested by Lewin Gan Lewin.

Thanks a lot to them and all others who are sending the problems or just ideas of the problems!

The problems D and E was prepared by Alexey Dergunov dalex. Other problems was prepared by me (Edvard Davtyan). I want to note the generator for the problem E its difficulty comparable with the solution to the problem F. Thanks to Maria Belova Delinur for checking the English statements. The problems was tested by users: unprost, Smaug, Aleksa Plavsic allllekssssa, Alexey Dergunov dalex and Lewin Gan Lewin. Thanks a lot to all of them!

I hope you will enjoy the problems!

P.S.: I really like the problem F and hope to see Accepted-s for it.

Good luck and have fun!

UPD: The contest is finished. The editorial is ready.

Hello.

Now it became much unlikely to skip a round due to carelessness during the registration. In the coming rounds (in experimental mode) we will add new feature extra registration (it is good terminology? additional registration?).

This means that after the period of regular registration (as usual, 5 minutes before the start of a round it will be closed) there will be another additional period of registration. It will start in 10 minutes after the start of the round with duration of 20 minutes, that is, it will close after 30 minutes from the start of the round.

The role of the 10 minutes is twofold:

• on the one hand it is quite possible to solve the easiest problem in the first 10 minutes — so it makes a motivation to register on time,
• on the other hand the system is loaded much during the first minutes of a round, as a registration invalidates some internal caches it is better to open extra registration after 10 minutes.

When registering during the extra time a participant is automatically assigned to a random room (among suitable for its role).

Hi everybody.

The IndiaHacks finals will take place tomorrow (on Saturday). The contest is being organized by HackerEarth. Just after the official finals, the CF round will start (check-your-time) with almost the same problems. You can treat it as a standard CF round — there will be 5 problems in each of 2 divisions, and 2 hours to solve them. Two divisions will compete together on the problem set with 7 problems, with 2 hours to solve them.

I want to especially thank I_love_Tanya_Romanova for testing the problems, GlebsHP for help with making the CF round possible, and MikeMirzayanov for his awesome attitude and for the Polygon system. Setters: Lewin, k790alex, Sokolov, Errichto. Testers: I_love_Tanya_Romanova, Errichto. Small help: belowthebelt, raviojha2105, johnasselta, Radewoosh. And my big thanks to HackerEarth for inviting me to Bangalore, it's truly a vibrant city.

Some info only for 40 official finalists — Remember not to discuss anything until the CF round ends (so, at least 2 hours after the official contest ends). You will find all important information at link-to-the-contest. You can ask me questions by PM on CF or on HE, and I will put answers in the "Challenge Details" at the link provided. Do not use comments here because it can only confuse others. You can use some old blog about the IndiaHacks semifinals if you want to discuss something.

I wish you great fun and no frustrating bugs. Enjoy the contest.

Scoring: 500-1000-1500-2000-2500-3500-3500.

WINNERS

1. jqdai0815, the only one to solve all 7 problems!
2. JoeyWheeler
3. jcvb
4. andrew.volchek
5. ikatanic

In the official finals there were technical issues with the stack size (it was again only 8MB) and constraints in E weren't correct at the beginning. We want to fix it as much as possible, without any guessing though — we can't say how much time did you waste because of something. If you were affected then write to me PM with the description of the situation. Your time penalties will be canceled (and maybe some earlier submission will be accepted, if only the stack size didn't allow you to get AC).

Editorial is being created here.

Hey Codeforces!

The Elimination Round of the CROC 2016 Championship will take place on Friday, March 18 at 16:35 UTC. After our last round, Yang Liu (desert97), Michael Kural (pi37) and I realized that we haven't had enough, so we joined forces with Kevin Sun (ksun48) and Daniel Chiu (waterfalls) to prepare another problem set for you guys. Our contest will be for combined divisions and consist of seven problems. And although only those who pass the Qualification Round can participate officially, the round will be open to and rated for all Codeforces users. As always, we'll be taking the tractor to Bovinia for some farmland algorithmic adventures with Farmer John, Bessie and her best friend Elsie!

Before we begin, we'd like to thank GlebsHP for doing a wonderful job as contest coordinator—we'd be hopeless without you. We would also like to thank MikeMirzayanov and the Codeforces staff for creating the awesome Codeforces and Polygon platforms. And finally, we're immensely grateful to abacadaea for providing one of the problem ideas and to winger and AlexFetisov for test solving our round.

Formally, there will be two rounds on the same problem set (both rated):

• CROC 2016 — Elimination Round: for registered Championship participants who have passed the Qualification,
• CROC 2016 — Elimination Round (Rated Unofficial Edition): for all others.

To take part in the official round you have to be registered for the Championship and solve at least one problem in Qualification round. Both the elimination round and its unofficial edition will be rated. The only difference is that the top 50 participants in the official round will be invited to join the Finals in Moscow. Finalists will be responsible for organizing their trip (tickets, hotel, visas and so on). Each participant may claim reimbursement for transportation expenses not exceeding ~135 USD. Invitations should be accepted no later than March 25.

We hope you enjoy our problems and our cow-flavored text even more than you did last time! Good luck!

UPD1: System testing is delayed because we are investigating some technical issues.

UPD2: The editorial has been posted here. Thanks for participating!

UPD3: Since last ~15 minutes judging system was incorrectly configured for F in the contest "CROC 2016 — Elimination Round" (it is interesting story how it happened), you may appeal your rating change if it affected you much. If you have submitted a solution for F in last 15 minutes and you have strong arguments why incorrect verdict (WA/RE on the test 1) significantly affected your place, please write MikeMirzayanov to make your participation unrated. Sorry about the issue. You can do it before March, 19, 23:59 (UTC).

UPD4: I'd like to congratulate the winners of each round, as well as the top 50 in the Elimination Round for progressing to the CROC 2016 Championship Finals! In addition, Petr and jqdai0815 deserve a special shoutout for solving all seven problems!

CROC 2016 — Elimination Round

1. Petr
2. tourist
3. vepifanov
4. rng_58
5. I_love_Tanya_Romanova

CROC 2016 — Elimination Round (Rated Unofficial Edition)

1. jqdai0815
2. anta
3. Alex_2oo8
4. NaiveNaive
5. eddy1021