مرحبا, Codeforces!

Translation: Hello, Codeforces!

We are super excited to invite you to participate in Codeforces Round 1007 (Div. 2), which will be held on Friday, February 28, 2025 at 17:35.

This round will be rated for all participants with rating below $$$2100$$$. Participants with higher ratings are encouraged to participate out of the competition.

You will be presented with $$$6$$$ or $$$7$$$ problems and $$$2$$$ hours and $$$15$$$ minutes to solve them. The problems are authored and prepared by Al-Merreikh, ApraCadabra, FetFot, limbo16, MOUFLESS, and Vectors_Master.

We would like to thank everyone who made this round possible:

• Sugar_fan for coordinating the round and helping with problem preparation.
• satyam343 for improving some problems and providing suggestions to help us make the round better.
• Our army of testers: StarSilk, fallleaves01, _istil, rui_er, N_z__, Error_Yuan, Kaitokid, Proof_by_QED, Boboge, The_Hallak, Wael_Zaiback, Igor_Parfenov, Mohanad_Nahhal, hocln, FTS_Problem_C, ALAov, BERNARB.01, BabaVoss, MaherSefo, satyam343, larush, purp4ever, ZaiBug, The_Weighted_MST, Nahhas, Shawerma, and spaghetti_coder for testing our round and providing invaluable feedback.
• MikeMirzayanov for the amazing Codeforces and Polygon platforms.
• Alexdat2000 for translating the statements into russian.

• You

  for participating in this round.

The score distribution will be as follows:

We hope you will find a non-empty subset of problems to be interesting. Good luck, have fun and see you in the standings on Friday!

Let's continue the series of announcements with a photo of the authors. We only managed to find one photo with three of us, another with two, and one with just a single person. Enjoy figuring out who’s who!

UPD: Congratulations to the winners!

All participants:

1. ksun48
2. maspy
3. potato167
4. jiangly
5. RGB_ICPC4

Rated only:

1. RGB_ICPC4
2. lequoctran181
3. LifeWillChange
4. VaVshchuck
5. ToffeeLong

UPD: Editorial has been posted. Check it out!

Hello Codeforces!

The series of Educational Rounds continues thanks to the support of the Neapolis University Pafos.

On Feb/27/2025 17:35 (Moscow time) Educational Codeforces Round 175 (Rated for Div. 2) will start.

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, Ivan BledDest Androsov, Maksim Neon Mescheryakov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Big thanks to the tester shnirelman for his valuable advice and suggestions!

Good luck to all the participants!

Our friends at Neapolis University Pafos also have a message for you:

Admission to the Computer Science and Artificial Intelligence bachelor's program at Neapolis University Pafos is open!

The JetBrains Foundation supports this bachelor's program and offers 15 fully funded scholarships for the most talented applicants. The scholarships cover tuition, accommodation, medical insurance, visa fees, and pocket money (€300 per month).

First admission round:

• Application deadline – April 23, 2025
• Entrance test – April 27, 2025

UPD: Editorial is out

Hi everyone!

ne_justlm, itz_pabloo and I would like to see you as participants of Codeforces Round 1006 (Div. 3), which starts at Feb/25/2025 17:35 (Moscow time).

The round will be held according to the rules of educational rounds. Thus, during the round, tasks will be tested on preliminary tests, and after the round there will be a 12-hour open hacking phase (we really hope that not too many solutions will fall during it).

How the next announcement is made:

• this is where copy-paste starts,

here is your text, icpc rules, etc.

• this is where copy-paste ends.

You will have 2 hours and 15 minutes to solve 7 problems. The penalty for an incorrect submission will be 10 minutes.

We remind you, that only reliable participants of the third division will be included in the official results table. As it is written on the link — this is a necessary measure to combat unsportsmanlike behavior. To qualify as a "trusted" member of the third division, you must:

• take part in at least two rated rounds (and solve at least one problem in each of them),
• don't have a point of 1900 or higher in the rating.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600 (or you are a newcomer/unrated), you may choose to participate rated or unrated.

We would like to thank MikeMirzayanov for the Codeforces and Polygon platforms, and Vladosiya for incredibly cool coordination of round preparation.

As well thank you very much we would like to say to Kirill_Maglysh for his huge help in creating this round.

Also thanks for our testers:

• Ormlis, isaf27 for nutella testing.

• tch1cherin, WLZ for red testing.

• Egorsa, shadow9236, cry, alexsushin, Sokol080808 for honey testing.

• Dck, FBI, pskobx for the illusory technique — purple!

• Ianis, kaferius_cf, NerfThis, ukhalikshina, umezo, Escapisst, hump-and-bump, Kosya for such a familiar and close, water testing.

• tih-a, mkshh, Pozercpp, Kraska, radodododo, giorgi_pkhaladze and I hope the universe will be merciful to you.

• myav, sujan_roy24, t.muksunov, imtheonly1, DevUt for pleasant natural testing.

UPD: EDITORIAL ON CF Editorial

The best and brightest programmers from around the world have gathered this week in Dongguan, China, for the highly anticipated 2025 Universal Cup Finals!

Event Details

• Date: Saturday, February 22nd
• Start time: 10:30 AM CST (2:30 AM UTC)
• See participating teams
• Full schedule can be found here

Streaming

Witness the best contestants in the world as they push the boundaries of skill and strategy. You can be part of this event by following us online either on English Channel or Chinese Channel.

Mirror Contest

Join the mirror contest and compete in real-time with the finalists from anywhere in the world. Any Universal Cup registered team can participate. The mirror contest is available here, you may use your Universal Cup team account or register a new account to participate in the mirror contest.

Stay Tuned for the Conference

This isn't just a competition – it's a global celebration of competitive programming. Join us for The 2025 Universal Cup Conference for Competitive Programming on Sunday, February 23rd. Listen to insightful discussions with the brightest minds in the field.

The Conference will be streamed on jiangly's channel.

Hello Codeforces!

The series of Educational Rounds continues thanks to the support of the Neapolis University Pafos. They offer a BSc in Computer Science and AI with JetBrains Scholarships. Gain cutting-edge skills in AI and machine learning, preparing you for high-demand tech careers. Curious? Check out the CSAI curriculum now. Limited scholarships available — don't miss your chance to study in Europe for free!

On Feb/18/2025 17:35 (Moscow time) Educational Codeforces Round 174 (Rated for Div. 2) will start.

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, 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

I am very excited to offer you to participate in Codeforces Round 1005 (Div. 2), starting at Feb/16/2025 17:35 (Moscow time).

There will be 6 very epic tasks and you will have 2 hours to solve them. All problems were authored and prepared by me. This round will be rated for all participants with rating below 2100.

I would like to thank the following list of orzosities for making this round possible:

• flamestorm for coordinating and helping with problem preparation.
• My army of testers: N_z__, triple__a, sammyuri, _istil, Dominater069, nifeshe, awesomeguy856, Error_Yuan, anango, temporary1, efishel, turska, Wxssim, amoeba4, Wizard_of_Orz, Proof_by_QED, myst-6, Friedrich, weirdflexbutok, That_Salamander, rewhile, Hori, vikram108, lowbob, doujinshi_master, redpanda, RobinFromTheHood, larush, Jasonwei08, beaten_by_ai, alwyn, chromate00, lucaski2, theweakestsilver.
• cry for not testing.
• MikeMirzayanov for codeforces and polygon.
• Alexdat2000 for translating the statements into russian.
• You for participating.

Good luck, have fun and I hope you have non-negative rating changes!

Score distribution: $$$500 - 1000 - 1250 - 1750 - 2250 - 2750$$$

UPD: editorial

UPD2: Congratulations to the winners!

From Div2:

1. KOPOLb_4YPOK
2. orzFesdrer
3. Octagons
4. nvnamson
5. KSCD

From Div1 and Div2:

1. potato167
2. kotatsugame
3. maspy
4. turmax
5. noya2

Hello again, Codeforces!

I am glad to invite you to Codeforces Round 1004 (Div. 1), Codeforces Round 1004 (Div. 2), at Feb/11/2025 17:35 (Moscow time).

In Division 1 you will be offered $$$6$$$ problems. In Division 2 you will be offered $$$7$$$ problems. One of the problems in Div.1 will be divided into 2 subtasks. Round duration is set to be 2 hours.

Also, both divisions contain at least one interactive problem(s), so be prepared for those! Guide for interactive problems

I would like to thank,

• FairyWinx for dedicated coordination, a lot of problemset discussion, and suggesting one of the problems idea.

• Our testers: Dart-Xeyter, teraqqq, RP-1, larush, Wansur, furt1ve, Iura_Shch, SomethingNew, Gabbasov, glllll, domovonok, Error_Yuan, Monogon, triple__a, evjeny_23, Blinov_Artemii, LeoPro, antontrygubO_o, A_G, N_z__, mainyutin for testing and providing feedback.

• MikeMirzayanov, KAN for Polygon and Codeforces platforms.

As always, we hope you will like the problems. Have fun!

Score Distribution:

Div. 1: $$$750$$$ — $$$750$$$ — $$$1250$$$ — ($$$750$$$ + $$$1250$$$) — $$$2000$$$ — $$$3000$$$

Div. 2: $$$500$$$ — $$$1000$$$ — $$$1250$$$ — $$$1750$$$ — $$$1750$$$ — $$$2250$$$ — $$$3000$$$

UPD: Editorial

UPD2: We sincerely regret to inform you that we have discovered a bug in the interactor. A series of tests is currently underway to assess the full impact of this issue. Once we have the results, we will provide a detailed update. We deeply apologize for this incident and any inconvenience it may have caused.

UPD3: After the analysis, it was determined that this problem affected a small number of participants. There are no submissions that get AC with the correct interactor and erroneously received a non-AC verdict earlier. Therefore, the following decision was made:

If your solution worked with the old interactor, but does not work with the correct one and your rating has decreased, then the round will be unrated for you.

UPD4: Congratulations to the winners!

Div.1:

1. Kevin114514

2. tourist

3. Radewoosh

4. turmax

5. heuristica

Also, special thanks and congratulations to rainboy for being one and only one solving problem F in division 1!

Div.2:

1. Morisz10

2. Wxssim

3. Aurora14526

4. shardulisgapryongkim

5. igAC

Codeforces!

Proof_by_QED, chromate00, larush, Edeeva, and I would like to invite you to participate in Codeforces Round 1003 (Div. 4), starting on 09.02.2025 17:35 (Московское время). We have baked $$$8$$$ problems to be solved in $$$2$$$ hours and $$$15$$$ minutes. We hope the problems will be interesting, unique...and skibidi.

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

• 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), you may choose to participate rated or unrated.

Large text, to get your attention for the following:

PLEASE NOTE the rule restricting AI use. If you are caught using AI in an unorthodox manner, either by us manually or detected automatically, YOUR ACCOUNT WILL BE TERMINATED. We will be actively scouring submissions and terminating rulebreakers.

Anyways, I would like to orz the following:

• Vladosiya for coordinating.

• Our growing family of testuwuers: [VIP] Dominater069, Error_Yuan, amoeba4, Intellegent, [VIP] Friedrich, temporary1, efishel, 18o3, -firefly-, __baozii__, monadtransformer, Sacharlemagne, Lilypad, kevlu8, Filikec, [VIP-] macaquedev, beaten_by_ai, mathtsai, DivinePunishment, pianapolataa, reirugan, and pop.

• MikeMirzayanov for running this site for 15 years. 15 years ago, I was still eating crayons.

UPD: Editorial

UPD2: Regarding Skipped Submissions