Hello, Codeforces!

I'm glad to invite everyone to Codeforces Round 1008 (Div. 1), Codeforces Round 1008 (Div. 2), which will be held on Mar/10/2025 17:35 (Moscow time).

You will be offered $$$7$$$ problems in both divisions 1 and 2, and you will be given $$$2$$$ hours and $$$30$$$ minutes to solve them.

Both divisions contain at least one interactive problem(s). Please look up the guide if you are unfamiliar with them.

I'd like to give my utmost thanks to

• satyam343 and Kaey for coordinating this contest, preparing statements/tasks, and donating a problem.

• The testers: Dominater069, LMeyling, Rhael, Mysticmage45, tigerBoss101, Non-origination, TyroWhizz, _istil, LipArcanjo, Error_Yuan, Proof_by_QED, ffao, NerfThis, ikrpprppp, Murinho, WLZ, Irmuun.Ch, Tainel, Chaska, marianoferesin, ankan2526, Darshan_Bhangale, kolomig0r, dougalves, profchi, Lucina, 0I0acOJleHbKa, Marckess, Saman., N_z__, PeruvianCartel, sammyuri, A_G, catology, arvindf232

• My friends Rhael for an illustration, Punpun (no CF account) for one task, and a shoutout to Mysticmage45 for no particular reason.

• Alexdat2000 for the Russian translation.

• MikeMirzayanov for Polygon and Codeforces platforms.

I hope everyone will indulge in the tasks blissfully.

Score distribution

Division 1: $$$500-1000-1500-2250-2250-2500-3000$$$

Division 2: $$$500-750-1250-1750-2000-2750-3500$$$

Oh hello there. This is chromate00, just casually on the announcement of Codeforces Round (Div. 3). And now, you see a drawing.

$$$\square$$$ — $$$\triangle$$$ — $$$\triangle$$$ — ◯ — $$$\triangle$$$ — $$$\square$$$ — $$$\triangle$$$

And then, you think. You see a square, a triangle, and a circle. Also, a Korean problemsetter. You immediately imagine the certain survival game that popped up in your memory. And you may be right. Or you might be wrong. Whatever, what I can ensure you is that you will be absolutely stunned to see the problems. Or astonished. You might not believe what you see. This round might change everything.

Anyways, the preface was a bit too long. Starting from Mar/11/2025 17:35 (Moscow time), you will be given $$$\mathbf{7}$$$ problems to be solved in $$$\mathbf{2.5}$$$ hours. There is at least one interactive problem, so I strongly urge you to read the guide if you are unfamiliar with the format.

The round will be hosted by rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of open hacks. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution but the usual penalty of 10 minutes for each wrong submission, following the rules of educational rounds.

Remind yourself 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)
• not have a rating of 1900 or higher at any moment in time.

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 (unless you register unrated).

Also, note the (relatively recent) rule restricting the use of AI. If you are caught while breaking this rule, you will be terminated.

This round is made possible by the help of the following people:

• cry and Vladosiya for coordinating the round (and translating the statements),
• Proof_by_QED for reviewing the tasks (and not so particularly testing them),
• Our army of (not so) pink soldiers: Intellegent, amoeba4, mathtsai, Error_Yuan, temporary1, Edeeva, yeetholmes619, hashman, larush, poi, (VIP) Dominater069, (VIP) LMeyling, (VIP-) macaquedev, antontrygubO_o, Mercuria, DivinePunishment, 0pt1mus23, pianapolataa, reirugan, efishel, (VIP) awesomeguy856, rewhile, __baozii__, yoru_sacri, -firefly-, sbreger60, monadtransformer, Rahuldeb5,
• The VVVIP, MikeMirzayanov, for great platforms Codeforces and Polygon.

I hope that you will also be in the spectacular moment.

Welcome to the final weekend of Codeforces Blitz Cup! More information about selection matches is available in this post, but we are now down to just 16 contestants! Here is how they will compete on Saturday and Sunday for the content and glory!

Saturday, March 8

1. turmax 25 : 20 b6e0: Mar/08/2025 13:00 (Moscow time) Scoreboard
2. errorgorn 31 : 2 izban: Mar/08/2025 14:10 (Moscow time) Scoreboard
3. isaf27 2 : 31 alireza_kaviani: Mar/08/2025 15:00 (Moscow time) Scoreboard
4. winners of 1 and 2: errorgorn 20 : 25 turmax: Mar/08/2025 16:00 (Moscow time) Scoreboard
5. Geothermal 35 : 10 jonathanirvings: Mar/08/2025 17:00 (Moscow time) Scoreboard
   ☕

6. heuristica 0 : 33 antontrygubO_o: Mar/08/2025 19:00 (Moscow time) Scoreboard

7. tourist 31 : 2 conqueror_of_tourist: Mar/08/2025 20:00 (Moscow time) Scoreboard
8. ksun48 20 : 13 Kuroni: Mar/08/2025 21:00 (Moscow time) Scoreboard
9. winners of 6 and 7: tourist 45 : 0 antontrygubO_o: Mar/08/2025 22:00 (Moscow time) Scoreboard
10. Golovanov399 33 : 0 induk_v_tsiane: Mar/08/2025 23:00 (Moscow time) Scoreboard

Sunday, March 9

• 11: winner of 3 and 5: alireza_kaviani 10 : 35 Geothermal: Mar/09/2025 15:00 (Moscow time) Scoreboard
• 12: winner of 8 and 10: ksun48 15 : 18 Golovanov399: Mar/09/2025 16:00 (Moscow time) Scoreboard
• 13: Semifinal: winner of 4 and 11: turmax 12 : 21 Geothermal: Mar/09/2025 17:00 (Moscow time) Scoreboard
• 14: Semifinal: winner of 9 and 12: tourist vs Golovanov399: Mar/09/2025 18:00 (Moscow time) Scoreboard Scoreboard2
• 14 rematch: tourist 27 : 18 Golovanov399: Mar/09/2025 19:20 (Moscow time) Scoreboard
• 15: Final match: winner of 13 and 14: tourist 45 : 0 Geothermal: Mar/09/2025 20:05 (Moscow time) Scoreboard

And the winner is

Congratulations tourist on winning the Blitz Cup 2025!

And huge thanks to lperovskaya, Vladosiya, tourist, MikeMirzayanov for organizing the event, as well as Egor and jonathanirvings for commentating most of the matches!

Tune into the live broadcast on youtube.com/@codeforceslive to see your favorite contestants compete and commentate!

Hello everyone!

Soon, the Open Olympiad in Informatics will take place, which you may know from the online mirror of last year or from the rounds 345, 469, 545, 626, 707, 775. This olympiad is prepared by Moscow Olympiad Scientific Committee. Archives from previous years, problems from qualifying stages, and other information can be found on the olympiad website inf-open.ru.

The Open Olympiad consists of interesting and difficult problems proposed by our authors' team. Therefore, we decided to conduct a non-rating mirror of the Olympiad on Codeforces. The Olympiad takes place in two rounds, each consisting of 4 problems, not ordered by difficulty, and 5 hours to solve them. The difficulty of the problems is comparable to the level of Div. 1. Each problem is worth 100 points that are distributed into multiple subtasks with different constraints that allow the participant to earn partial score. Testing is done in the IOI format, where the participant receives a full testing report on all tests in the Online-subtasks during the competition. The feature of the Open Olympiad is that some problems have Offline-subtasks, the results of which will only be available after the end of the competition. Note, that you will not have access to the scoreboard during the competition.

The mirror on Codeforces will take place in Mar/07/2025 11:05 (Moscow time) and Mar/10/2025 11:05 (Moscow time).

The competition problems were created and prepared by Kapt, allvik66, stepanov.aa, Mangooste, AgafonovArtem, dyrbulshchyl, RP-1, valerikk, yunetive29, Kniaz, Alexdat2000 guided by Mangooste, grphil and Helen Andreeva. Special thanks to Tikhon228 for his contribution to the preparation of the problems.

Special thanks to MikeMirzayanov for the codeforces and polygon systems, which were used in preparing the problems for this Olympiad.

Many thanks to the Olympiad testers: Ormlis, isaf27, allvik66, AgafonovArtem, RP-1, Qwerty1232, kostylevGO, katyaporay, FairyWinx, a.stepanov281005, EgorUlin, pakhomovee, ArtAlex, Sweezy, Be_dos, valerikk, alexsushin, Dart-Xeyter, yunetive29, AndreyPavlov, Mikhango, v0s7er.

Good luck!

UPD1: The results of the first day are available.

We’re excited to launch the first-ever Midnight Code Cup (MCC) — a team competition featuring an online Qualification round and a 24-hour onsite Final. Expect algorithmic challenges, optimization puzzles, cutting-edge computer science, and some just plain weird problems. It’ll be exhausting. And fun.

Who are we?

A team of problem solving geeks veterans enthusiasts, eager for the return of this contest format. The idea of Midnight Code Cup was born at Recraft.AI (AI image generation and graphic design pioneers) with huge support from JetBrains (creator of Kotlin, intelligent IDEs, and AI-driven developer tools) as well as Neon (developer-first open-source database) and Pinely (HFT company powered by competitive programmers).The sponsor list is not final and will be updated.

We are also thankful to have Codeforces as our hosting partner.

Who can participate?

Teams of 3 ready to rock and roll! No programming language, affiliation or problem solving methods restrictions. You only need to be at least 18 years old and have a slightly concerning enthusiasm for coding challenges.

Save the Date

April 12, 2025: Online Qualification (5 hours) – here at Codeforces

June 7–8, 2025: Onsite Final (24 hours) – Belgrade, Serbia

Problem setters and jury: Aksenov239, isaf27, NALP, Taube, Gassa, cdkrot, PavelKunyavskiy, tourist, qwerty787788, MaxBuzz, pvs, Solenoid555, nsychev, naagi

Registration opens soon – you have enough time to find a team. Leave your email here and you will be the first to register.

See you at Midnight!

The European Championship 2025 will take place on the 2nd of March in Porto. The top teams from the European ICPC regionals CERC, NWERC, SEERC, SWERC will compete for the title of European champions. It is the second edition of this ICPC super-regional.

The mirror contest European Championship 2025 - Online Mirror (Unrated, ICPC Rules, Teams Preferred) will be held on Codeforces at Mar/02/2025 13:35 (Moscow time) and will last 5 hours.

The mirror contest will feature the same problems as the official competition, except for one problem, which will be presented in a more challenging version.

I am the chief judge for the competition and I want to thank:

• The amazing set of judges who proposed and prepared the problems: bicsi, cip999, cdkrot, Egor, gangsterveggies, Giove, Jorke, Petr, thocevar.
• Our beloved tester ksun48.
• Everyone involved in the organization of EUC, in particular our director Fernando Silva.
• The developers of DOMjudge, the contest system used in the official contest.
• MikeMirzayanov for Polygon (that we used to prepare the problems) and for letting us host the mirror on Codeforces.

I invite you to participate in the contest and I hope that you will like the problems.

On the difficulty
The contest features problems with difficulties from div1A to div1E. It should be enjoyable for many, and interesting even for the strongest teams in the world.

Rules

1. The contest is unrated, so your codeforces rating will not be affected.
2. The scoring is ICPC-style: teams are first sorted by number of problems solved, then the time-penalty is used as a tie-break. An incorrect submission gives a 20 minutes penalty.
3. We encourage participation as a team.
4. If you are participating in a team, we encourage you to use only one computer for coding the solutions (as in an ICPC contest). Regarding using templates, googling, and copy-pasting code: feel free to do it.

UPDATE 1: Here you can find the editorial: https://codeforces.net/blog/entry/140239

UPDATE 2:

Congratulations to the winners, and especially to the first team for AK:

1. [?]: LeoPro, fastmath, turmax
2. jiangly
3. [HoMaMaOvO] hos.lyric, maspy, maroonrk

Hi,

We would like to invite you to participate in the live online mirror contest of The 2025 ICPC Asia Pacific Championship next weekend. ICPC Asia Pacific Championship is the contest for top non-winning teams from all regional contests in the region to qualify to the World Finals. See the region rules and competition page for more details.

The official contest is scheduled to start at Saturday, 1 March 2025, 10am (UTC+8). The live online mirror contest is scheduled to start only 5 minutes later, to keep both contests run almost in sync. The contest is 5 hours long and consists of several problems.

Please note that we might have to postpone the live online mirror contest in case the official contest is delayed. This is to the ensure that the tasks are not available to the public until the official contest starts.

The contest will use ICPC-style scoring (same as the official contest) and will be unrated. You can participate as an individual or as a team, although as a team of three members is preferred.

See you on top of the leaderboard.

The 2025 ICPC Asia Pacific Championship Judges

[UPD]: Task analysis: https://apac.icpc.global/assets/competition/problem-analysis.pdf

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, FzArK, 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, ammar2000, ALAov, too_rusty, BabaVoss, MaherSefo, satyam343, larush, purp4ever, ZaiBug, The_Starry_Night, ginger.swap02, 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. SuRiNonSul
3. lequoctran181
4. LifeWillChange
5. tuamitk42

UPD: Editorial has been posted. Check it out!