Hello Codeforces!

On Apr/22/2022 17:35 (Moscow time) Educational Codeforces Round 127 (Rated for Div. 2) will start.

Series of Educational Rounds continue being held as Harbour.Space University initiative! You can read the details about the cooperation between Harbour.Space University and Codeforces in the blog post.

This round will be rated for the participants with rating lower than 2100. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.

You will be given 6 or 7 problems and 2 hours to solve them.

The problems were invented and prepared by Adilbek adedalic Dalabaev, Vladimir vovuh Petrov, Ivan BledDest Androsov, Maksim Neon Mescheryakov and me. Also huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

UPD: Editorial is out

Hello Codeforces!

SlavicG, flamestorm, MikeMirzayanov, Errichto, and I want to invite you to the long-awaited second Div. 4 round!

It starts on Apr/21/2022 17:35 (Moscow time).

The format of the event will be identical to Div. 3 rounds:

• 5-8 tasks;
• ICPC rules with a penalty of 10 minutes for an incorrect submission;
• 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
• after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
• by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).

We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.

Only trusted participants of the fourth division will be included in the official standings table. This is a forced measure for combating unsporting behavior. To qualify as a trusted participant of the fourth division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them),
• do not have a point of 1400 or higher in the rating.

Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), then the round will be rated for you.

Many thanks to the testers: senjougaharin, magnus.hegdahl, Vladosiya, MeGustaElArroz23, Sho, bakekaga, geranazavr555, doreshnikov, jampm, Neophiliatic, qwexd and VIP-tester _Vanilla_.

We suggest reading all of the problems and hope you will find them interesting!

Good Luck!

Update: Editorial

Hello Codeforces!

I am happy to invite you to Codeforces Round 783 (Div. 2), and Codeforces Round 783 (Div. 1) which will be held on, Apr/19/2022 17:35 (Moscow time)! This round is rated for both divisions.

I would like to thank the following people who made the round possible:

• Aleks5d for coordinating the round!
• KAN for reviewing the problems.
• 4qqqq, YashDwivedi, k_balint, Riladavin, Peti, Akulyat, kclee2172, errorgorn, dorijanlendvaj, KAN, gamegame for testing the round and giving valuable feedback.
• MikeMirzayanov for great Codeforces and Polygon platforms.
• NEAR for supporting the Codeforces community! Details can be found in this post.
• You for participating!

In each division there will be 6 problems and 2 hours to solve them.

Score distribution:

Div. 2: 500 — 500 — 750 — 1500 — 2000 — 2500.

Div. 1: 250— 1000 — 1500 — 2000 — 2750 — 3500.

Good luck!

UPD: Editorial

UPD2: Congratulations to the contest winners:

Div. 2:

1. HenHenHenAAAAAAAAAAAAA

2. QiangBro_ShuDe

3. MarioPariona117

4. Moomer

5. SpadeA261

Div. 1:

1. djq_cpp

2. tourist

3. maroonrk

4. Um_nik

5. Rewinding

Hello, Codeforces!

TimeWarp101 and I are excited to invite you to Codeforces Round 782 (Div. 2) which will take place on Apr/17/2022 17:35 (Moscow time). This round will be rated for participants with rating lower than 2100.

Many thanks to all the people who made this round possible:

• Arpa and KAN for coordinating the round!
• KAN for Russian translations.
• AwakeAnay for a lot of advice throughout the process + listening to my terrible problem ideas, and for proposing tasks that did not make it to the final problemset.
• TimeWarp101 cause I love you uwu <3
• i_am_completely_useless for being completely useless.
• antontrygubO_o, AmShZ, AwakeAnay, generic_placeholder_name, TeaTime, fishy15, TheScrasse, kartikeyasri23, MagentaCobra, _Vanilla_, Etherite and Codula for testing and providing detailed feedback that improved the quality and balance of the round significantly.
• Our lord and saviour MikeMirzayanov for great systems Codeforces and Polygon.
• NEAR for supporting the Codeforces community! Details can be found in this post.

You will have 2 hours to solve 6 problems.

Scoring distribution: $$$500-750-1500-2000-2250-3000$$$

We've tried to keep the statements short and pretests strong. We hope you will enjoy the round!

See you all in the standings!

P.S. namanbansal013 will be livestreaming his solution explanations for some of the problems here. Do check out his channel too!

UPD: We are really sorry for the issues with the queue, but we hope you liked the problems anyway.

UPD: Editorial

UPD: Congratulations to the winners!

Official winners:

1. Fire_big
2. 20333333333
3. _DAC_
4. SILA_edr
5. Nutella3001

Unofficial winners:

1. Geothermal
2. disorientation
3. Koosha_Mv
4. tute7627
5. oleh1421

First solves:

1. A: SSRS_ at 00:01
2. B: SSRS_ at 00:03
3. C: PurpleCrayon at 00:07
4. D: noimi at 00:17
5. E: CoderAnshu at 00:21
6. F: rainboy at 01:06

Hello.

In the meantime, the onsite event has already begun. You can follow the results at the link https://nerc.itmo.ru/archive/2021/standings.html (refrain from viewing if you want to plan to write a mirror and want the conditions as close as possible to the participants in the competition).

There is great news. This year it was possible to get together without any online participation. Teams write from one computer! Good old ICPC.

And I suggest you join the online mirror. It is designed for team participation by those who have passed the qualifying competitions. Ready to try? Use the link: 2021-2022 ICPC, NERC, Northern Eurasia Onsite (Unrated, Online Mirror, ICPC Rules, Teams Preferred).

Good luck!

Hello Codeforces!

On Apr/09/2022 17:35 (Moscow time) Educational Codeforces Round 126 (Rated for Div. 2) will start.

Series of Educational Rounds continue being held as Harbour.Space University initiative! You can read the details about the cooperation between Harbour.Space University and Codeforces in the blog post.

This round will be rated for the participants with rating lower than 2100. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.

You will be given 6 or 7 problems and 2 hours to solve them.

The problems were invented and prepared by Adilbek adedalic Dalabaev, Vladimir vovuh Petrov, Ivan BledDest Androsov, Maksim Neon Mescheryakov and me. Also huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

UPD: Editorial is out

Dear Codeforces Community,

Kirill22 and I are glad to invite you to Codeforces Round 781 (Div. 2), which will take place on Apr/08/2022 17:35 (Moscow time). This round will be rated for the participants with rating lower than 2100

These are some great people that we would like to thank:

• Artyom123 for round coordination (and KAN too!) and being in touch all the time for providing help
• Igorbunov, generic_placeholder_name, nskybytskyi, AlperenT, FairyWinx, TheScrasse, Ziware, vsinitsynav, wery0, Kotehok3, YanikusGG, Absyarka, FelixDzerzhinsky, Codula for testing and providing tons of feedback and making completely different submissions
• MikeMirzayanov for Codeforces and Polygon
• NEAR for supporting the Codeforces Community! You can find the details in this post.

You will have 2 hours to solve 5 problems.

One of these problems is interactive, please see the guide of interactive problems if you are not familiar with it.

The scoring distribution: 500 — 750 — 1250 — 1500 — 2250

P.S. I have been waiting for a long time to hold another contest and now this time has come. I really hope that you will like the problems, good luck!

UPD: Editorial

Hello.

I started processing responses on the form where we collected your TON wallet addresses. Unfortunately, many winners did not complete the form. I contacted some of them in PM and it turned out that this was not intentional.

We are extending the deadline for completing the form until 2022-04-06 23:59:59 (UTC +3). Please, if you want to receive coins, then fill out the form. A valid address looks like a random 48-character string. To register a wallet, follow one of these links: https://tonkeeper.com/ or https://wallet.ton.org/

The form can be filled out at https://codeforces.com/userForm/203c74605996e40f

Coins will be received by those who are at the top-1000. Additionally, those who solved at least one problem in this round will receive 1 coin each. Details can be read at the link.

The form will be processed on April 7th. And in a week after it, we will send out coins. Please do not disturb me or the organizers with questions that are answered in this post.

Also I remind you about TON Smart Challenge contest aimed at contract source code optimization: https://t.me/toncontests/26 It's not too late to connect and try your hand

You can read more about this competition here:

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.

Hello! Codeforces Round 780 (Div. 3) will start at Mar/31/2022 17:35 (Moscow time). You will be offered 6-8 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating of 1600 or higher, can register for the round unofficially.

The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of open hacks.

You will be given 6-8 problems and 2 hours and 15 minutes to solve them.

Note that the penalty for the wrong submission in this round is 10 minutes.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participant of the third division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them)
• do not have a point of 1900 or higher in the rating.

Thanks to NEAR for supporting this round, details can be found in this post.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of our work. Problems have been created and written by ITMO University team: MikeMirzayanov, MisterGu, myav, Gol_D, Aris, senjougaharin and Vladosiya.

We would like to thank: arvindr9, hocky, lucasxia01, Evirir, Sorting, 244mhq, yorky, Jostic11, sansen, leaf1415, Masha237, amr_abdelazim, coderbd, gs17005, nebula for testing the contest and valuable feedback. List of testers will be updated.

Good luck!

UPD: Editorial