Hello, Codeforces!

On Mar/11/2024 17:35 (Moscow time) Codeforces Round 933 (Div. 3) will start.

You will be offered 7 problems, dedicated to the adventures of a restless mathematician, a programmer and just a funny character named Rudolf and his brother Bernard, and 2 hours 15 minutes to solve them. Problems have 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.

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. 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.

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.

Problems have been created and written by: vladmart, Sasha0738, t0rtik, Alexey_Parsh, Mordvin13, daha.002, Vladosiya and natalina.

We would like to thank:

1. Vladosiya and Gornak40 for coordinating the round.

2. MikeMirzayanov for Polygon and Codeforces platforms and helping prepare the problems.

3. step_by_step, ashmelev for red testing.

4. KseniaShk, senjougaharin for yellow testing.

5. robotolev, Sochu for purple testing.

6. dan_dolmatov, SashaT9, FBI, SpicyOctopus for blue testing.

7. Gargera0, Matrosk1n, Alex_TULGU, Alenochka, gas for cyan testing.

8. bugrova, Toy_mouse, ringku_ for green testing.

Good luck!

UPD: Because of the technical issue (see the post https://mirror.codeforces.com/blog/entry/126654), temporarily the only available C++ compilers are: C++14 (GCC 6-32) and C++17 (GCC 7-32).

UPD2: Editorial is posted.

Hi everybody,

In a few days there will be a Moscow Open Olympiad. This olympiad is prepared by Moscow Olympiad Scientific Committee that you may know by Moscow Olympiad in Programming, Moscow Team Olympiad, and Megapolis Olympiad (rounds 327, 342, 345, 376, 401, 433, 441, 466, 469, 507, 516, 541, 545, 567, 583, 594, 622, 626, 657, 680, 704, 707, 727, 751, 775, 802, 829, 852).

The Open Olympiad consists of the most 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 competition problems were created and prepared by Mangooste, vaaven, Tikhon228, ViktorSM, isaf27, TheEvilBird, sevlll777, Papaz239 и pakhomovee guided by Ormlis, grphil and Helen Andreeva.

The mirror on Codeforces will take place in Mar/08/2024 12:05 (Moscow time) and Mar/09/2024 12:05 (Moscow time).

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: dshindov, FelixDzerzhinsky, Adikolon, isaf27, adepteXiao, talant, AgafonovArtem, Dart-Xeyter, inhabitant, Kapt, Siberian, alexashkins, alexxela12345, Sweezy, v0s7er, MOHOXPOM, Titoffifee.

Good luck!

UPD1: The solutions were tested on offline-groups. The scoreboard for the first day is also available.

UPD2: The solutions were tested on offline-groups. The scoreboard for the second day is also available.

UPD3: Combined scoreboard

Hello, Codeforces! 😇

We are glad to invite you to participate in Codeforces Round 932 (Div. 2), which will take place at Mar/05/2024 17:35 (Moscow time) 🔥 😱 🤩

The round has been fully prepared by students of the School CPM 💓 (School of the Pedagogical Skills Center): IzhtskiyTimofey, AndreyPavlov, and myself. The theme of all the problems will be our beloved school 😈

This round will be rated for participants with a rating below 2100 😊 Participants with a higher rating can take part out of competition 😋

We would like to thank 💕:

• Our wonderful coordinator Artyom123 for helping prepare the problems and valuable advice! 😍

• CPM students azureglow and max0000561 for proposing problems 😎

• Our teacher grphil for nurturing young talents 💋

• TheEvilBird and NToneE for creating wonderful contests for the superhard group 🤮

• Geothermal for detailed feedback on the problems and improving the quality of the statements in English 💘

• Our testers A_G, SomethingNew, induk_v_tsiane, zwezdinv, k1sara, meowcneil, antonis.white, maomao90, MOHOXPOM, qualdoom, makrav, sergeev.PRO, Kihihihi, DimonKrutoi, htetgm, tiom4eg, Mikhango, MrEssiorx, adepteXiao, YakovLya, sunsh1ne, AVdovin, Egorsa, mishgun, dasha..zhilina, marzipan, kaido, jgjgjjg, mkshh, Makarchik_228, Nikitun for suggestions to improve the problems 😘

• MikeMirzayanov and the entire Codeforces team for creating the wonderful platforms Codeforces and Polygon 💖 💙 💚 💛

You will be offered 6 problems and 2 hours to solve them! We tried to make interesting, beautiful, NP-complete problems with strong pretests 😁

Score distribution: $$$500 - 1000 - 1500 - 1750 - 2500 - 3000$$$ ✨

We wish everyone good luck in the round, and we would also like to wish good luck to the participants of the upcoming Open Olympiad in Informatics and ROI! 🥇

UPD: Editorial

UPD 2: Congratulations to the winners!

Div. 2:

1. Sakura_lenlen

2. keeping_practicing

3. INeedCarb

4. LJL_T

5. yyyz04

Div. 1:

1. tourist

2. jiangly

3. BurnedChicken

4. m_99

5. Sugar_fan

We apologize for the disbalance in our problemset. However, we hope these problem fun and interesting!

Hi,

We would like to invite you to participate in the live online mirror contest of The 2024 ICPC Asia Pacific Championship next weekend. ICPC Asia Pacific Championship is a new playoff round introduced to the Asia Pacific region this year. It 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, 2 March 2024, 9am (UTC+7). 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 official contest will be livestreamed here and the scoreboard can be accessed here.

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 2024 ICPC Asia Pacific Championship Judges

UPD1: The official contest is postponed by (at least) 30 minutes, so the mirror contest is postponed similarly.

UPD2: The official contest is postponed by 20 minutes (instead of the originally announced 30 minutes) after its original schedule, but the mirror contest is still scheduled to start 30 minutes after its original schedule to avoid more confusion.

UPD3: The analysis is available here

Hello, Codeforces!

I invite you to participate in Codeforces Round 931 (Div. 2), which will be held on Mar/01/2024 17:35 (Moscow time).

The round will be rated for participants with rating lower than 2100. Participants with higher rating can participate in round unofficially.

You will have 2 hours to solve 5 problems, with one of the problems having 2 versions. One or more interactive problems may occur in the round, so please read guide for interactive problems before the contest.

All problems are authored by me.

I would like to thank:

• Akulyat for round coordination and help with preparation

• A_G, okwedook, rui_er, jdurie, lunchbox, _rey, wjli, .-O_O-., aryanc403, akshaykhandelwal, PartTimeCoder, carnation13, its_pranjal_83, Ianlsam, Immerser, vikram108, praneeth6116, soham976roy, and Dev_30 for testing the round and providing useful feedback.

• MikeMirzayanov for Codeforces and Polygon platforms.

Good luck to all participants!

UPD: Score distribution: 500 — 1000 — 1500 — (1500 — 1250) — 3250

UPD2: Editorial

UPD3: Congratulations to the winners!

Div1 + Div2

Div2

"You are braver than you believe, stronger than you seem, and smarter than you think." — A.A. Milne

Hello Codeforces!

I have the pleasure of inviting you to participate in Codeforces Round 930 (Div. 1) and Codeforces Round 930 (Div. 2), which will start on Feb/29/2024 17:35 (Moscow time).

You will be given 6 problems and 2 hours to solve them in both divisions.

One of the problems may be interactive. So, please refer to the guide on interactive problems if you are unfamiliar with them.

The problems were prepared and authored by wuhudsm, chromate00, Psychotic_D and MagicalFlower.

We would like to thank :

• irkstepanov for coordinating the round;
• BurnedChicken for the only LGM testing;
• amenotiomoi,siganai, vgtcross, amethyst0, dognotlike, alireza_kaviani, and dorijanlendvaj for GM and IGM testing;
• aryanc403, k1r1t0, Little_Sheep_Yawn, Amir_Parsa, blxst, pavlekn, Error_Yuan, IceKnight1093, aufannn, Mingyu331, Akulyat, Arpa, and mhtkrag for M and IM testing;
• O--O, Abhishek_Srivastava, MrDelrus, htetgm, Silver_Fox, dhyang24, and milind0110 for CM testing;
• brave-kid, adventofcode, vikram108, mafailure, AnanasClassic, Yugandhar_Master, FD..LH..lloyJ, lemoncookie, and flakes24 for Expert testing;
• Banis, stepan.karpov, BF_OF_Priety, and ONEHUNDREDPUSHUPS for Specialist testing;
• HexShift for the only Pupil testing;
• JaberSH1 for the Newbie testing;
• tibinyte for the Illegal newbie lying face testing;
• MikeMirzayanov for the great Codeforces and Polygon platforms;
• And at last but not least, You for participating in the round!

Good luck, and may the code be with you!

UPD: Score distribution:

Div.1: $$$500 - 1000 - 1500 - 2000 - 2500 - 2750$$$

Div.2: $$$500 - 1000 - 1500 - 2000 - 2500 - 3250$$$

UPD2: Let's continue the streak of announcements with photos of the authors and coordinator.

UPD3: Editorial is out.

UPD4: Top Performers

Div.1

Div.2

“It is not important to be better than someone else, but to be better than you were yesterday.” — Master Oogway, Kung Fu Panda

Hello, Codeforces! We are proud to present Codeforces Round 929 (Div. 3), and we hereby invite all of you to take part in it. This round will start on Feb/27/2024 17:35 (Moscow time). You will have 2 hours and 15 minutes to solve 7 problems. The penalty for a wrong submission is equal to 10 minutes.

This round will be rated for participants with ratings lower than 1600. However, all of you who wish to take part and have a rating of 1600 or higher, are welcome to 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.

Remember that only the trusted participants of the third division will be included in the official standings table. As stated in this blog, this is a compulsory measure for combating unsporting behaviour and upholding gracious professionalism. 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.

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.

The problems were authored and prepared by erniepsycholone, snowysecret, dbsbs, jerryliuhkg, lomienyeet, and our beloved coordinator Vladosiya.

We would like to thank:

• Vladosiya for his high-speed coordination;

• arvindf232 for Legendary Grandmaster testing;

• step_by_step for International Grandmaster testing;

• physics0523, culver0412, AHappyPotato for Grandmaster testing;

• pavlekn for Master testing;

• moonpie24, anthony123, mariowong123 for Candidate Master testing;

• peshkoff, ksodp, SashaT9, Elison, MoLotfi for Expert testing;

• DBSHoShunNgai, Doncho_Bonboncho for Specialist testing;

• myvaluska, dbsMarco, dbsptl for Pupil testing;

• CannotPupil, KyleLeungHS for Newbie testing;

• MikeMirzayanov for creating Codeforces and Polygon.

We hope that this contest, regardless of your background, rating and result, will increase your exposure to competitive programming and make you better than you were yesterday. Have fun!

UPD: Let's continue the streak of announcements with photos of the authors. This time with our coordinator and testers :)

UPD2: We discovered the screencast from Um_nik a short while before the end of the contest, and it had around 400 views by the end of the contest. Round is still rated, however, people who have used his solutions will be punished.

UPD3: Editorial is out

Hello Codeforces!

On Feb/23/2024 17:35 (Moscow time) Educational Codeforces Round 162 (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, Roman Roms Glazov 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

mesanu, SlavicG and I are very excited to invite you to Codeforces Round 928 (Div. 4)! It starts on 19.02.2024 17:35 (Московское время). We would also like to give a very special thanks to the efforts of MikeMirzayanov and Vladosiya, who helped significantly with the preparation of the round!

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.

Thanks a lot to the testers: MADE_IN_HEAVEN, Gheal, Dominater069, Phantom_Performer, Vladosiya, htetgm, hbarp, tvladm!

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

UPD: Editorial is posted!

Hello! On Feb/18/2024 15:05 (Moscow time) will start Codeforces Round 927 (Div. 3), the next Codeforces round for the third division.

The round is based on problems from JetBrains Academy Youth Challenge. If you participated in it, please don't participate in this round.

Problems for this round are prepared by denk, step_by_step, goncharovmike, ikrpprppp, pashka, Vladosiya and MikeMirzayanov.

Thank you very much awoo, BledDest, buyolitsez, EgorUlin, Gojova, GrandFruit, Hello_zoka, petyb, scanhex, senjougaharin, shnirelman, SomethingNew, Toy_mouse, Zandler for testing the round.

As usual for the third division rounds:

• there will be 6-8 tasks in a round
• round duration is 2 hours 15 minutes
• the round follows the ICPC rules, penalty for an incorrect submission is 10 minutes
• round is rated for participants with ratings up to 1600
• after the round there will be a 12-hour open hacking phase

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 behaviour. 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.

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.

Good luck to all!

UPD: Editorial