Hello, Codeforces!

It's been a long journey, and I'm finally pleased to invite you to participate in our Codeforces Round 955 (Div. 2, with prizes from NEAR!), which will take place on Jun/25/2024 17:35 (Moscow time).

This round will be rated for all participants with a rating is below 2100. Participants with higher ratings can participate out of competition.

During the round, you will need to solve 6 problems. You will have 2 hours to solve them.

The problems for the round were prepared by nik1998, egor4444ik, iamdimonis and me.

We sincerely thank everyone who provided invaluable assistance in preparing this round:

• Our insightful coordinator 74TrAkToR for excellent communication, helpful advice and assistance in problem preparation!
• Kolychestiy for improving one of the problems.
• EJIC_B_KEDAX, A_G, zwezdinv, Dominater069, culver0412, TheScrasse for red testing.
• Kolychestiy, CSQ31, exhausted, azureglow, harsh__h, meowcneil for yellow testing.
• onlytrall, veleboks, zarubin, robotolev, TimVen74, Vladosiya for purple testing.
• Alenochka, LightSky, Chugunov_Alexander, slash0t, PoDuReMaN, katzi, Vamperox, redpanda for blue testing.
• Matrosk1n, bessarab, dariasaligina, GRIVA_, viteli, dazlersan1 for cyan testing.
• Kirillar2, Sonya_2009, dan00ile for green testing.
• venlesN for gray testing.
• MikeMirzayanov for the wonderful Codeforces and Polygon systems.

We are pleased to announce that NEAR has supported the round!

NEAR was founded in 2017 by Illia Polosukhin, one of the creators of Transformers, and Alex Skidanov as an attempt to build an artificial system capable of solving competitive programming problems. You can read more about that attempt here.

Ultimately, NEAR pivoted into building a blockchain protocol, which it launched in 2020.

This year, NEAR started NEAR.AI, a new lab with a mission to build AI systems that are open and available to everyone, instead of being controlled by a few mega-corporations.

One of the areas of focus is making models capable of reasoning reliably, and for that, competitive programming problems provide a great environment. To help us build it, we invite all the Russian-speaking members of the Codeforces community with a rating of Specialist or higher (1400+) to help us annotate step-by-step explanations of solutions to competitive programming problems. We want to annotate a very large set of problems of all difficulty levels, and pay relatively high rewards in NEAR per annotation. Don't speak Russian but speak English? Stay tuned here, we will be launching the same project for English-speaking people very soon, and will likely sponsor another round when it happens.

The round also features prizes in NEAR. Participants who rank in the top 16 will receive Ⓝ 16 each. The next 32 participants in the overall ranking (including unofficial participants) will receive Ⓝ 8 each. The following 64 participants will receive Ⓝ 4 each; the subsequent 128 participants will receive Ⓝ 2 each, and finally, the next 256 participants will receive Ⓝ 1 each.

Additionally, 64 random participants from the top 4096 in the overall ranking will each receive Ⓝ 4.

Score distribution: $$$500\,—\,1000\,—\,1000\,—\,1750\,—\,2500\,—\,3000$$$

Wishing everyone good luck and high ratings!

UPD: Let's continue the series of announcements with a photo of the authors :)

Hello! Codeforces Round 954 (Div. 3) will start at Jun/23/2024 17:50 (Moscow time). You will be offered 7 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 7 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.

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 tasks were created and prepared by 74TrAkToR. I would like to thank everyone who helped me a lot with round preparation.

• Coordinator Vladosiya for excellent communication and brilliant coordination of the round!
• Testers veleboks, iNNNo, Sk0rlupka, sharkycode, Noobish_Monk, meowcneil, Matrosk1n, sumit_kk10, Sonya_2009, FelixArg, KirillKhalin, viteli, zwezdinv, EJIC_B_KEDAX, _why_not_, detective...dots, Leeda, windreaper for high-quality testing and valuable advices!
• MikeMirzayanov for amazing Codeforces and Polygon platforms!

Good luck!

UPD: Editorial

This weekend, we will host the 2nd Universal Cup Semifinal. Unlike with previous Universal Cup rounds, there will be exactly one window that all teams will participate in. This window will be from 5pm to 10pm UTC+8 on Sunday, June 23rd. Note that this window is after the onsite version.

Any Universal Cup registered team can participate. If you are new here, please register following the instructions on Registration.

Besides competing to advance to the Universal Cup Finals, sponsored by Huawei, we have also prepared prizes for teams in the top 10 (excluding onsite teams in the Summer Summit) . The prize details are as follows (may be replaced by products of similar value):

After the online semifinal, we will host a stream of all onsite teams competing in the Semifinal at the Summer Summit event in Cancun, along with problem analysis. The stream will start immediately after the end of the online version at 10pm (UTC +8) and end at 3am (UTC +8). We will run livestreams in English and in Chinese as follows:

• English: YouTube through tourist's account!

• Chinese: Bilibili through jiangly's account!

Who are you cheering on to win the onsite Semifinals? Here are the teams:

We look forward to your participation!

Hi everyone!

Sponsored by

We are happy to announce that Osijek camp will be returning this Autumn, on August 31-September 8 2024, right before the ICPC World Finals 2024 on 15-20 September 2024 in Astana, Kazakhstan. The camp is hosted by the School of Applied Mathematics and Computer Science of the University of Osijek and is brought to you by the organizing team of adamant and -is-this-fft-.

The camp is inspired by various competitive programming camps that we attended during our active years in ICPC, and is aimed to help college students prepare for ICPC regional contests and finals. The camp will consist of 7 ICPC-style contests and 2 days off.

Details

Participation fee for onsite participants is 150€ per person. It does not include regular meals, travel or accommodation. Some further details about location, travel and food options can be found on the website.

If you want to participate, but are unable to come onsite, we offer a reduced fee of 100€ per person for online participation. It is also possible to reduce fees individually if you are unable to attend some of the contests. This will be handled on a case-by-case basis.

We support and empathize with those affected by the ongoing war in Ukraine, therefore we offer a 100€ discount for affected individuals and teams affiliated with Ukrainian institutions. In other words, the fees would be 50€ and 0€ per person for onsite and online participation correspondingly.

The expected starting time for the contests is 10am CET. For online participants, it is still a preferred starting time, but we will make accommodations for virtual participation at a later time, whe really necessary.

Most of our contests are originally developed for the camp. A small number of contests may be based on previous contests that have not been released to the general public. If you have seen some problems of a contest before, you can't participate on that day. We will privately contact participants who might be affected.

After the camp, we will have a silence period during which camp materials will not be released to the public. We ask participants not to discuss the problems in public unless they obtained an explicit permission from contest authors.

Participants

If you are interested in participating, please fill the form here.

We ask you to register before August 23 if you want to participate online and before August 16 if you want to participate onsite.

Also, if your university or organization has a lively ICPC community that may be interested in attending the camp, and you have some contacts of people in charge (e.g. coaches) we would highly appreciate if you could share some details in a direct message to me (adamant) or Tähvend (-is-this-fft-). Thanks!

Problemsetters

We'd like to thank and praise the authors of the contests in the camp:

• conqueror_of_tourist — ICPC 2022 world finalist. Codeforces LGM in Python.
• tfg — ICPC 2018 and 2019 World Finalist, sqrt decomposition enjoyer and the person that optimized the intended complexity of 1508F - Optimal Encoding.
• Farhod — Codeforces IGM, 2x IOI silver medalist, hates ad hoc problems.
• Amtek — CERC 2022 and 2023 champion. ICPC 2023 and 2024 finalist.
• jacynkaa — CERC 2022 champion. ICPC 2021 and 2023 finalist.
• teapotd — CERC 2019 and 2021 gold medalist. ICPC 2020 and 2022 finalist.
• wuhudsm — Codeforces Master, maintainer of TheForce community, author of over 100 competitive programming problems.
• chromate00 — Problemsetter of 28 tasks on Baekjoon, also known for blogs reinventing the wheel several times.
• ToxicPie9 — ICPC 2021 and 2022 finalist. Authored more geometry than non-geometry problems.
• Mustang98, BigBag, Barichek, Denisov, Valera_Grinenko — ICPC World Finals 2020 bronze medalists, SEERC 2023 champions.
• Kevin114514, yaoxi_std, JCY_, Daniel_lele, ducati, Evier., WaReTle, J.Doe, schrodingerstom — students of Nanjing Foreign Language School.

... And others. We would also like to thank Arpa, two times ICPC World Finalist and former Codeforces Contest Coordinator, for his help with reviewing problem proposals. You can find more details about contest rules and technical setup on the website.

Special thanks

Finally, we say special thanks to

• our sponsors, who make the camp possible;
• ICPC foundation for their help and support;
• Codeforces for guidance and promoting this announcement to the main page;
• eolymp for providing an online judge for the contests;
• School of Applied Mathematics and Computer Science of the University of Osijek for the invaluable help and providing a physical location for the camp.

Hello, Codeforces! We're glad to invite you to take part in Codeforces Round 953 (Div. 2), which will start on Jun/16/2024 12:05 (Moscow time). Note the unusual start time of the round. You will be given 6 problems and 2 hours to solve them.

This round will be rated for participants whose rating is below 2100. Participants with higher rating can participate unofficially.

The problems were authored and prepared by Artyom123, IzhtskiyTimofey, bashkort, TheEvilBird, 127.0.0.1, Tikhon228 and me.

The round is based on All-Russian olympiad in the name of Keldysh.

We would like to thank

• Artyom123 for his high-speed coordination;
• A_G, culver0412, AlexRex0, harsh__h, CSQ31, PMiguelez, dazlersan1, htetgm, oaoaoa_mmm, FynjyBath, Mikhango, Ormlis for testing;
• MikeMirzayanov for creating Codeforces and Polygon.

Score distribution: $$$500 - 750 - 1250 - 1500 - 2000 - 2500$$$

UPD: Editorial

Hellowo Codeforcers :3

sum and I are very delighted, ecstatic, enchanted, euphoric, excited, exultant, jubilant, overjoyed, and proud to invite you to participate in Codeforces Round 952 (Div. 4), which will start on Jun/11/2024 17:35 (Moscow time). There will be $$$8$$$ problems, with one split into two subtasks, to be solved in $$$2.5$$$ hours.

As usual, I have to copy and paste the following...

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.

We want to express overwhelming gratitude to the following individuals for making the contest possible:

Vladosiya and mesanu for coordinating the contest and reviewing the problems.

Dominater069, omeganot, Phi-001, flamestorm, nskybytskyi, willy108, ScarletS, mark, yuan-shen, vgoofficial, htetgm, buffering, yash_9a3b, haochenkang, ETL, natalina, MatthewC3297, and lcsc0 for testing the round.

MikeMirzayanov for the usual.

We suggest reading all of the problems as we have put mucho effort into all of them. Best of luck, mis amigos!

UPD: Editorial

Hello, Codeforces!

We are pleased to announce Codeforces Global Round 26! Thanks to XTX Markets for supporting the initiative! In 2024, we are holding 4 such rounds. The series results will take into account the best 3 participations out of 4.

On Jun/09/2024 17:35 (Moscow time) we will host Codeforces Global Round 26.

Codeforces Global Round 26 marks the second round in the 2024 series of Codeforces Global Rounds. These rounds are open and rated for everyone.

The prizes for this round are as follows:

• The top 30 participants will receive a t-shirt.
• 20 t-shirts will be randomly distributed among participants ranked between 31 and 500, inclusive.

The prizes for the 4-round series in 2024:

• In each round, the top-100 participants get points according to the table.
• A participant's final score will be the sum of the points they earned in their 3 highest-placing rounds.
• The top 20 participants across the series will receive sweatshirts and placement certificates.

We extend our gratitude to XTX Markets for supporting the global rounds initiative in 2024!

The problems were written and prepared by null_awe, flamestorm, le0n, and buffering.

We would also like to thank:

• Our amazing coordinator TheScrasse for his quick and thorough review.
• Our last-minute Russian translator Alexdat2000.
• Our testers bronze_coder, conqueror_of_tourist, Ra16bit, Flamire, Esomer, PurpleCrayon, Ritwin, awesomeguy856, Tekor, Sugar_fan, htetgm, sum, lunchbox, Ste, liympanda, CSQ31, oursaco, Edlue, eggag32, Tsotne533, serichaoo, Mononoke001, redpanda, janY_, tiagodias, pablopalou, S2speed, cry, Marckess, madlogic for their rigorous feedback.

Round Information:

• Duration: $$$3$$$ hours
• Number of problems: $$$8$$$ problems
• Score distribution:
  $$$500 - 750 - (750 + 1250) - 2500 - 3000 - 3000 - 4000 - 5000$$$

We eagerly anticipate your participation!

UPD: Editorial! https://codeforces.com/blog/entry/130252

UPD2:

Winners!
1. tourist
2. jiangly
3. Benq
4. jqdai0815
5. Nachia

First Solves
A: Benq
B: Thienu
C1: nwn
C2: Benq
D: Be_dos
E: Tom66
F: kiwihadron
G: tourist
H: rainboy

Hello, Codeforces!

I am glad to invite you to participate in Codeforces Round 951 (Div. 2), which will take place at Jun/06/2024 17:35 (Moscow time).

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

You will be offered 6 problems and 2 hours to solve them! Interactive tasks may occur in the round. Please read this blog to get familiar with this type of problems.

All tasks are authored and prepared by me. However, I'd like to thank Greg908 for discussing ideas about problems and useful feedback!

I would like to thank:

• Artyom123 for his amazing coordination!

• 74TrAkToR for the initial help with this round.

• isaf27 for LGM testing.

• dorijanlendvaj, A_G, Mangooste, andrei_boaca and BucketPotato for red testing.

• ArtAlex, salyg1n, Kihihihi, 127.0.0.1, max0000561, ilyakrasnovv and a.nasretdinov for orange testing.

• Semen07 for purple testing.

• newb_programmer for blue testing.

• A1st for cyan testing.

• ishaandas1 for green testing.

• TimoSvyato and HatakeyamaLeo for grey testing.

• MikeMirzayanov and the entire Codeforces team for creating the wonderful platforms Codeforces and Polygon.

The goal was to create problems interesting to solve. Hope you'll enjoy them all!

Score distribution: $$$500 - 1000 - 1500 - 2000 - 2500 - 3000$$$;

Good luck!

UPD: Congratulations to the winners!

Div. 2:

1. Tanikaze_Amane

2. olmrgcsi

3. PMPuns

4. MegalovaniaJ

5. Sylphrena

Div. 1 + Div 2:

1. turmax

2. jiangly

3. kotatsugame

4. peti1234

5. BurnedChicken

Editorial is out!

Hello! Codeforces Round 950 (Div. 3) will start at Jun/03/2024 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. After open hacks all accepted solutions will be rejudged on successful 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.

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 our team: myav, Gornak40, senjougaharin and Vladosiya.

We would like to thank:

1. MikeMirzayanov for help with ideas and Polygon and Codeforces platforms.

2. Be_dos, Dominater069, 74TrAkToR, BucketPotato for red testing.

3. KseniaShk, cry, tolbi, ScarletS, nskybytskyi, sevlll777 for yellow testing.

4. mahdi.hasnat, Phantom_Performer, mainyutin for purple testing.

5. natalina, FBI, Kopite, MADE_IN_HEAVEN, mz1 for blue testing.

6. Romakolesn for cyan testing.

Good luck!

P.S.: We are aware of the error that occurred while updating the ratings for Educational Codeforces Round 166. It will be fixed before this round. UPD: We fixed it!

UPD: Editorial is out!

Hello, Codeforces!

We are glad to invite you to participate in Codeforces Round 949 (Div. 2), which will start on May/31/2024 13:05 (Moscow time). Note the unusual start time of the round. You will be given 6 problems and 2 hours to solve them.

This round will be rated for participants whose rating is below 2100. Participants with higher rating can participate unofficially.

The problems were authored and prepared by sinsop90, yinhee and me.

I would like to thank:

• 244mhq for his wonderful coordination.
• sinsop90 and yinhee for providing problem ideas and discussing the problems with me.
• AFewSuns and crazy_sea for providing a better solution to one of the problems.
• Um_nik for the only LGM testing.
• A_G, antontrygubO_o, StarSilk, CharlieV, rui_er and Andreasyan for red testing.
• FengLing, YuJiahe, CSQ31, small_peter and JWRuixi for orange testing.
• yinhee, QwQwf, lovely-ckj, wsc2008qwq and Jryno1 for purple testing.
• sinsop90, dieselhuang, Edwin__VanCleef, wtc, WRuperD, starrykiller and gdf_yhm for blue testing.
• Ender32k and liangbowen for cyan testing.
• ishaandas1 for the only green testing.
• cyz2010 and cppcppcpp3 for grey testing.
• MikeMirzayanov for the great Codeforces and Polygon platforms.
• Last but not the least,

  You

  , for participating!

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

Good luck & Have fun!

UPD: Congratulations to the winners!

Div 2:

1. cyb0101
2. Feduk_Pro_Spb
3. whale_0086
4. graphcity
5. grass8cos

Div. 1 + Div. 2:

1. maspy
2. Savior-of-Cross
3. Rubikun
4. femboy-wannabe
5. turmax

Editorial and also Simplified Chinese Editorial are out.