By 1-gon, history, 3 weeks ago, In English

omg hi!

I am pleased to invite you to participate in Codeforces Round #712 (Div. 1) and Codeforces Round #712 (Div. 2)! You will be given 6 problems and 2 hours 15 minutes to solve them. I'm happy to announce the theme of this round is déjà vu!

I would like to thank the following people:

Make sure you read all problems, and I'm happy to announce the theme of this round is déjà vu! Good luck, have fun!

The score distribution will be announced immediately because you deserve it ❤️:

Div. 1: 750 — 1000 — 1250 — 1750 — 2500 — 4000

Div. 2: 500 — 1000 — 1750 — 2000 — 2250 — 3000

UPD: Editorial

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By Nickolas, 5 weeks ago, In English

The contest is over; I hope you enjoyed it! The editorial is available here.

The 9th April Fools Day Contest will take place on Thursday April 1st. 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.

Good luck, and have fun!

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By sigma_g, history, 4 weeks ago, In English

Hello all!

We are proud to invite you to CodeCraft-21, which takes place on Mar/29/2021 17:35 (Moscow time). It is rated for all Div2 participants (rating under 2100).

This contest comes under Threads'21, as a part of our annual techno-cultural fest Felicity, IIIT Hyderabad. We have special prizes for Indian participants!

You will be given six problems to solve in a duration of two hours.

We have tried our best to keep clean statements, useful samples with good explanations, and strong pretests! We have written step-wise editorials, and will also release video editorials!

We would like to thank these amazing people for helping make the contest happen:

There will be an interactive problem! You are recommended to read the corresponding guide.

We hope you enjoy the contest as much as we did preparing it! Good luck!

Update: The scoring distribution is 500/1000/1750/2500/2500/3000.

Update: Editorial is up! Video editorials available on our YouTube channel.

We are sorry for the sudden increase in difficulty from C to D. Nonetheless we hope you enjoyed the problems! :)

PRIZES: The following twenty lucky participants receive a tshirt:

  • top 10 Indian participants
  • random 10 from top 100 (ranks 11-100) Indian participants

These ranks are determined from the combined unofficial ranklist. We are coordinating with the CF team for the tshirt design, and we'll update the blog post when it is finalized. We also have INR 7K worth prizes exclusively for IIIT-Hyderabad students!

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By Supermagzzz, 4 weeks ago, translation, In English

Hello, Codeforces!


Hello! Codeforces Round #710 (Div. 3) will start at Mar/25/2021 17:35 (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 1600 or higher, can register for the round unofficially. The round will be hosted by rules of educational rounds (extended ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.

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

Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) 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 trusted participants of the third division, you must:

  • take part in at least two 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 for this round were invented by MikeMirzayanov, Supermagzzz, Stepavly and sodafago.

Thanks to darkkcyan, bugdone, harlequen, iankury, bfs.07, songsinger, infinitepro, sodafago, Gassa, Rox, sharepoLOVEDDD for testing this round.

Thanks to MikeMirzayanov for platforms and coordination of our work. Good luck!


UDP: Editorial is ready

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By JetBrains, history, 4 weeks ago, translation, In English

Hello Codeforces!

The sixth round of the Kotlin Heroes series recently finished! All the rounds are available to be used for practice here: Episode 1, Episode 2, Episode 3, Episode 4, Episode 5: ICPC Round and Episode 6). Thanks to everyone who participated – you inspire us to work even harder on the problems for the next round, and we think you’re really going to like them!

Congratulations to the top three contestants:

  1. tourist
  2. Egor
  3. Tlatoani

A Kotlin Heroes t-shirt and exclusive Kotlin stickers will be presented to:

  1. tourist
  2. Egor
  3. Tlatoani
  4. eatmore
  5. uwi
  6. Benq
  7. Geothermal
  8. TadijaSebez
  9. Maripium
  10. Maksim1744
  11. pashka
  12. Heltion
  13. dalt
  14. galen_colin
  15. tabr
  16. SYury
  17. natsugiri
  18. Golovanov399
  19. Spheniscine
  20. Discombobulated
  21. Ra16bit
  22. Aidos
  23. yudedako
  24. nuip
  25. knightL
  26. golikovnik
  27. wifiiii
  28. Fortin
  29. majk
  30. WiwiHo
  31. Bench0310
  32. wu_qing
  33. Kuyan
  34. Nikitosh
  35. cjtoribio
  36. receed
  37. vadimmm
  38. SecondThread
  39. LeoPro
  40. rapira
  41. Lily
  42. nhho
  43. PavelKunyavskiy
  44. abc864197532
  45. tatyam
  46. Heart_Blue
  47. Ji_Kuai
  48. darnley
  49. Potassium
  50. 353cerega

These participants also won branded t-shirts:

  1. polingram
  2. Prateek
  3. rotavirus
  4. linjek
  5. pr3pony
  6. ostroumov
  7. harshrajani460
  8. xiaowuc1
  9. arvindf232
  10. illyakr
  11. Jetman
  12. Leksiq
  13. IceKnight1093
  14. procrastinate7
  15. man.yasakov
  16. Viktor36
  17. matvey.kazakov
  18. cmplx-xyttmt
  19. SourabhYelluru
  20. daisy_2000
  21. stanm
  22. cristian1997
  23. SerVB
  24. aaronsms
  25. chick_magnet
  26. Ditmarscehen
  27. My_password_is_qwerty123
  28. Misha_Help
  29. Sohsoh84
  30. igla
  31. ans_human
  32. mystic777
  33. __RANI
  34. staffle
  35. MissNick
  36. arpit_malhotra
  37. penad
  38. I_love_Anya_Prokopyeva
  39. son8bon
  40. RandYan
  41. adimiclaus15
  42. babkabass
  43. KKT_89
  44. nishuz
  45. BMking
  46. KEKWait
  47. Kerpoo
  48. pineapple_pasta
  49. GlobalElite
  50. aka2910

We will contact the winners soon to coordinate the delivery of your prizes!

Special thanks goes to SecondThread for streaming the solutions of the entire practice round. Check out this wonderful tutorial:

If you are still new to Kotlin but want to give it your all in the next round, take a look at Basic Kotlin (solve Koans), Kotlin Playground, this tutorial, and these videos on competitive programming in Kotlin.

We wish you all the best and hope you enjoy coding with Kotlin!

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By KAN, 5 weeks ago, translation, In English

Hi everyone!

The Final Round of Technocup 2021 starts this Sunday, March 21, 2021 at 13:00 MSK (10:00 UTC)!

For those who want to compete on the same problems, we will hold two regular Codeforces Rounds in the evening: one for the first division, and another one for the second. The rounds are starting at Mar/21/2021 16:20 (Moscow time).

If you are a participant of the official Technocup Finals, you are not allowed to take part in the rounds in the evening. We ask participants of the official Finals not to discuss the problems in open media till evening.

The problems are prepared by: Alexander Golovanov399 Golovanov, Evgenii amethyst0 Belykh, Andrey AndreySergunin Sergunin, Alexey Aleks5d Upirvitskiy, Diego Diegogrc Garcia and me.

Also huge thanks to Bench0310, kokokostya, Um_nik, dorijanlendvaj, brunomont, Stepavly, antontrygubO_o, scnucjh, Nebuchadnezzar, wucstdio, golikovnik, kuviman, dantrag, BledDest, Supermagzzz, Maripium, geranazavr555, divanik, psevdoinsaf, Roms for testing and invaluable comments, and also to antontrygubO_o for the help in holding the mirror rounds.

Good luck!

Congratulations to winners of Codeforces Rounds!

Div. 1:

  1. ecnerwala
  2. Radewoosh
  3. Benq
  4. mango_lassi
  5. AliShahali1382

Div. 2:

  1. qwqc
  2. gezlik
  3. yanyutao
  4. fengqiyuka
  5. ykl

Thanks for participation! Editorial.

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By awoo, history, 5 weeks ago, translation, In English

Hello Codeforces!

On Mar/18/2021 17:50 (Moscow time) Educational Codeforces Round 106 (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 Roman Roms Glazov, 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!

Our friends at Harbour.Space also have a message for you:

Codeforces and Harbour.Space

Dear Codeforces!

We are coming with another scholarship opportunity to share with you. This time, our scholarship is targeted towards the brightest women in the community.

As you might know, March is the month where the whole world celebrates women. At Harbour.Space we want to use this opportunity to encourage more women to join the tech world and challenge the gender-bias in this field.

We believe that gender equality in the workplace starts with gender equality in the classroom. For that reason, we are offering our Women in Tech Scholarship. The scholarship consists of:

  • 50% off the yearly tuition fee: covers around €29,000 for bachelors and €11,450 for masters.
  • 32% off the application fee: €85 instead of €125

You can find more information about the scholarship here.



Make sure to apply before March 31st to benefit from the scholarship and discount.

Don’t hesitate to share this opportunity with any bright women in your personal circle as well. A simple share can help us transform someone's life.

We are always happy to see Codeforce members join the Harbour.Space family.

Keep in touch and follow us on LinkedIn for more scholarship opportunities. And follow us on Instagram to stay in touch with our student life, events, and success stories from our students.

Good luck on your round, and see you next time!

Harbour.Space University

Congratulations to the winners:

Rank Competitor Problems Solved Penalty
1 dlalswp25 6 128
2 Maksim1744 6 138
2 DreamingLeaf 6 138
4 nuip 6 149
4 kotatsugame 6 149

149 successful hacks and 1485 unsuccessful hacks were made in total!

And finally people who were the first to solve each problem:

Problem Competitor Penalty
A pavement 0:01
B PCTprobability 0:04
C PCTprobability 0:08
D Parliament 0:09
E KaladinStormblessed 0:17
F 718_MiL 0:10
G rainboy 1:27

UPD: Editorial is out

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By shishin, history, 6 weeks ago, translation, In English

Hello again, Codeforces!

Artyom123 and I are happy to invite you to Codeforces Round #708 (Div. 2), which will take place on Mar/17/2021 17:35 (Moscow time). This round will be rated for the participants with rating lower than 2100

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

You will have 2 hours to solve 5 problems (and 2 subtasks). This time the statements are not related to Valorant, but we still play it sometimes.

We hope that you will like all problems and you won't face any troubles during the contest. Good luck!

The scoring distribution: 500750(750 + 500)1750(1500 + 1500)

UPD: Editorial

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By MikeMirzayanov, 6 weeks ago, In English

Hello, Codeforces!

I understand that 2021 has been going on for a long time, but here I have picked up a subset of some of the improvements that the Codeforces team made in 2020. Soon I will publish numbers (no, charts) with statistics for 2020. In the meantime, I bring to your attention a list of changes and improvements.

By the way, this is a decent list. This is about half to a quarter of all changes. It's just that other changes are more often somewhere in the internals of the system and are not visible to users. Please read this list. Each item is the effort of someone from the team. Thanks to geranazavr555, kuviman and cannor147 for their efforts. You've made our platform better! Well, by the way, I don't quit programming and many improvements were made by me.

The items on the list are written in a concise and informal form, many of the items I just copied from commit messages from git. If you want more details — ask in the comments, we will tell you! Of course, I forgot to include some improvements in the list.

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By ch_egor, 6 weeks ago, translation, In English


Right now happens the first tour of the Open Olympiad in Informatics, and tomorrow will be the second one. This contest is prepared by Moscow Olympiad Scientific Committee that you may know by Moscow Team Olympiad, Moscow Olympiad for Young Students and Metropolises Olympiad (rounds 327, 342, 345, 376, 401, 433, 441, 466, 469, 507, 516, 541, 545, 567, 583, 594, 622, 626, 657, 680, 704).

Open Olympiad consists of the most interesting and hard problems that are proposed by a wide community of authors, so we decided to conduct a Codeforces regular round based on it, which will happen on Mar/13/2021 12:05 (Moscow time) and will be based on both days of the Olympiad. Each division will have 6 problems and 2 and a half hours to solve them.

We kindly ask all the community members that are going to participate in the competition to show sportsmanship by not trying to cheat in any manner, in particular, by trying to figure out problem statements from the onsite participants. If you end up knowing some of the problems of Moscow Open Olympiad (by participating in it, from some of the onsite contestants or in any other way), please do not participate in the round. We also ask onsite contestants to not discuss problems in public. Failure to comply with any of the rules above may result in a disqualification.

Problems of this competition were prepared by Akulyat, KiKoS, wrg0ababd, Nebuchadnezzar, biection, alexX512 isaf27, ismagilov.code, DebNatkh, Siberian, NiceClock guided by cdkrot, vintage_Vlad_Makeev, GlebsHP, Zlobober, meshanya, ch_egor, grphil, voidmax, Endagorion and Helen Andreeva.

Thanks to adedalic and KAN for the round coordination, statement translation and preparation of problems for the second division, and also thanks for MikeMirzayanov for systems Codeforces and Polygon, which was used to prepare problems of this olympiad.

Also thanks to 4qqqq and Aleks5d for providing an additional problems that helped to create (I hope) a balanced problem set for the round, and Um_nik for testing!

Good luck everybody!

Due to the official competition source codes of other participants will not be available for an hour after the end of the round.


Please do not discuss problems publicly until 12:30 UTC.

The scoring distribution for both divisions is not standard:

  • div1: 750 — 750 — 1500 — 2000 — 2500 — 3000
  • div2: 500 — 1000 — 1750 — 1750 — 2500 — 3000

UPD2: Editorial

UPD3: Winners!

Div. 1:

  1. tourist
  2. jiangly
  3. maroonrk
  4. ecnerwala
  5. Miracle03

Div. 2:

  1. wudi2016
  2. ShimaRin
  3. fengqiyuka
  4. gezlik
  5. b___

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