Note the unusual start time of the round.

Hello, Codeforces!

Now that Gaokao is over, we are very glad to invite you to participate in CodeTON Round 5 (Div. 1 + Div. 2, Rated, Prizes!), which will start at Jun/24/2023 17:05 (Moscow time). You will be given 9 problems and 3 hours to solve them. The round will be rated for everyone.

All problems are written and prepared by Gary2005, Asuka, Crying, sjcsjcsjc, MonkeyKing, DerekFeng, KbltQaQ, ShmilyTY and me.

Statements and editorials will be available in Chinese (Simplified) after the contest.

We would like to give our sincere thanks to:

• errorgorn for his wonderful coordination!
• Alexdat2000 for translating problem statements.
• gyh20, wangziji, MagicalFlower, themoon, qiuzx, Atomic-Jellyfish, valeriu, nvmdava, mtw, AlperenT, ffao, AquaMoon, Umi, zengminghao, blobugh, Arraiter, FengzhuJian, He_Ren, LZDQ, CrTsIr, Pineapplello, feecle6418, 1.618, Alexdat2000, tzc_wk, WAtoAC2001 and tibinyte for testing this round and providing valuable feedbacks.
• MikeMirzayanov for the great codeforces and polygon platform.
• Lastly, we would like to express our gratitude to you for participating in the round.

The main character of the problems will be Tenzing Tsondu.

We hope that everyone can enjoy the round! As this round is sponsored, everyone will have an opportunity to win some prizes!

Good luck!

UPD1: Here is the score distribution:

250 — 500 — 1000 — 1500 — 2000 — 2500 — 3000 — 3750 — 5000

UPD2: Tutorial is available.

UPD3: Congratulations to the winners.

1. tourist
2. maroonrk
3. hos.lyric
4. cnnfls_csy
5. Um_nik
6. DearMargaret
7. jiangly
8. potato167
9. kotatsugame
10. noimi

UPD4: Congratulations to the first solver of each problem.

A: alexwice
B: ksun48
C: PinkieRabbit
D: Um_nik
E: Qingyu
F: amenotiomoi
G: tourist
H: rain_boy
I: maroonrk (after contest)

UPD5: Chinese statements

UPD6: Chinese editorials

Some information from our title sponsor:

Hello, Codeforces!

We, the Ton Foundation team, are pleased to support CodeTON Round 5.

The Open Network (TON) is a fully decentralized layer-1 blockchain designed to onboard billions of users to Web3.

Since July 2022, we have been supporting Codeforces as a title sponsor. This round is another way for us to contribute to the development of the community.

The winners of CodeTON Round 5 will receive valuable prizes.

The first 1,023 participants will receive prizes in TON cryptocurrency:

• 1st place: 1,024 TON
• 2–3 places: 512 TON each
• 4–7 places: 256 TON each
• 8–15 places: 128 TON each
• …
• 512–1,023 places: 2 TON each

We wish you good luck at CodeTON Round 5 and hope you enjoy the contest!

Hello, Codeforces!

On Jun/20/2023 17:35 (Moscow time) Codeforces Round 881 (Div. 3) will start.

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.

Problems have been created and written by: zwezdinv, EJIC_B_KEDAX, molney, Sokol080808, meowcneil, Vladosiya.

We would like to thank:

1. Vladosiya for coordinating the round.

2. MikeMirzayanov for Polygon and Codeforces platforms and testing.

3. tute7627 for red-black testing.

4. ace5, sevlll777, oursaco, lightseba, gmusya, pavlekn, vrintle, tolbi for yellow testing.

5. diskoteka, moonpie24, SashaT9, shell_wataru, MGod, Phantom_Performer, tarattata1, alex.kudryashov, Restricted, sdyakonov for purple testing.

6. Alex239, MrEssiorx, olyazyryanova, marzipan, Pa_sha, Rudro25, azureglow, IHateGeometry, ivan.alexeev, krigare for blue testing.

7. Guevara74, ctraxxd for cyan testing.

8. sahal, exhausted, viteli, prohamer80 for green testing.

Good luck!

UPD: Editorial.

With a special dedication to all the people from Ukraine.

Hi, Codeforces!

I have the pleasure of inviting you to participate in Codeforces Round 880 (Div. 1) and Codeforces Round 880 (Div. 2), which will start on Jun/18/2023 17:35 (Moscow time). You will be given 6 problems and 2 hours to solve them in both divisions.

The problems were authored and prepared by Arti1990, Okrut, w0nsh, kempusss, Fly_37, kobor, maras, and me. As the tasks are based on problems from Polish Championship in Team Programming for High School, which takes place earlier on the same day, participants from the original competition are asked not to participate in this round nor share the problems.

I want to thank:

• 74TrAkToR for coordination, the round wouldn't be possible without him;
• Alexdat2000 for translating problem statements;
• jacynkaa, oogerbooger, Swistakk, natofp, GreatEagle, Grzmot, Maliniarz, viki88830, AlexLuchianov, Little09, Ecrade_, Kieray, pshat, piratZnachor, piegusek, E_huan, njupt_lyy, p_b_p_b, KeNaj712, Lavine, RUSH_D_CAT, and AquaMoon for testing and many, many advice how to make this round better;
• MikeMirzayanov for Codeforces and Polygon platform!

The scoring distribution:

Div. 1: $$$500$$$ — $$$1250$$$ — $$$1500$$$ — $$$1750$$$ — $$$2250$$$ — $$$3000$$$

Div. 2: $$$750$$$ — $$$1000$$$ — $$$1250$$$ — $$$2000$$$ — $$$2250$$$ — $$$2750$$$

Editorial

Have fun and good luck!

Hi!

This Sunday will take place All-Russian olympiad for students of 5-8 grades, in the name of Keldysh. Good luck to all the participants! This contest is prepared by Moscow Olympiad Scientific Committee that you may know by Moscow Team Olympiad, Moscow Olympiad for Young Students, Moscow Open Olympiad in Informatics (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, 857).

We are happy to announce Codeforces Round 879 (Div. 2) based on the problems of this olympiad! It will be a Div. 2 round, which will take place at Jun/18/2023 11:05 (Moscow time). Please notice the unusual time. You will have 6 problems and 2 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 All-Russian olympiad in the name of Keldysh (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 grphil, Mangooste, sevlll777, Siberian, TeaTime, teraqqq, Ziware, TheEvilBird, Ormlis, Alexdat2000, vaaven, Mikhango, Artyom123 guided by Ormlis, grphil and Helen Andreeva.

Thanks to Artyom123 for the round coordination, and also thanks to MikeMirzayanov for systems Codeforces and Polygon, which was used to prepare problems of this olympiad.

Great thanks to the testers of the round: PurpleCrayon, He_Ren, feecIe6418, penguinhacker, ix35, Dominater069, MagicalFlower, tzc_wk, gyh20, ezraft, Kieray, AquaMoon, satori_____, njupt_lyy, Mike4235, ak2006, Lavine, Ritwin, xiaossr, turmax, fastmath, Kapt, Kirill22, Be_dos, Olerinskiy, gmusya, blyat, vsinitsynav, orz, TheGoodest, playerr17, lesssia.

UPD1: Scoring distribution:

500 – 1000 – 1250 – 1750 — 2500 – 3000

Good luck everybody!

UPD2: Editorial

UPD3: Winners!

Official:

1. Final_Brave_Niuniu
2. tzc___________________wk
3. MoFalkmusic
4. do_while_not_not_true
5. Cherrt

Unofficial:

1. hank55663
2. stkwill
3. jiangly
4. Sugar_fan
5. Brovko

Hello Codeforces!

On Jun/12/2023 17:35 (Moscow time) Educational Codeforces Round 150 (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 Adilbek adedalic Dalabaev, Ivan BledDest Androsov, Maksim Neon Mescheryakov, Dmitry TheWayISteppedOutTheCar Piskalov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Additionally, big thanks to the testers ashmelev, shnirelman and Fanarill for their valuable advice and suggestions!

Good luck to all the participants!

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

Hello Codeforces,

Thinking about what to do with your one wild life? You are amazing in every way imaginable! You are young and immensely talented, so why not setting yourself up for a lifetime adventure — studying abroad with Harbour.Space University. Our experienced ICPC coaches are looking for new talent to join the Harbour.Space teams in SWERC and Asia Pacific regions.

Every year and all around the year, Harbour.Space University is offering full and partial Bachelor and Master scholarships to study in Barcelona and Bangkok for the academic year 2023/24 for all aspiring and eligible ICPC candidates. We qualified 2 times for the ICPC world finals and it is only the beginning of skills deployment for Spacers.

Sign up using this form to be invited to join our week-long summer camp in Spain, to get to know each other and meet the HS faculty and staff.

Our upcoming Welcome Camp will take place in August 1-7, nearby Barcelona.

After we spend a week together, you can be offered a place to study at our university. You don’t even have to leave Spain after the camp, if you secure an offer.

This is your real chance to experience two amazing cities with people from all over the world and get a diploma and accreditation too. Study, compete, work, travel, teach, enjoy the sun, sea, mountains, and all these while networking with the legends of competitive programming, future high-tech entrepreneurs and famous startup investors.

We are a no nonsense university that will immerse you into the international culture and spirit of adventure, improve your English and help you build unprecedented confidence and technical expertise to ace the ICPC. With us, you can do what you love everyday, as we never force you to take courses that you do not find interesting! When we say full academic freedom, we mean it. Your personal growth and everyday development are our utmost priority. We recognise your special abilities and therefore needs, everyone at Harbour.Space is unique and here for a reason.

Our caring admission officers are always there for you to answer any questions you might have about studying and working in Barcelona or Bangkok campuses.

Come and help us build the university of the future. Join the Stars.

Lana Velikanova, The Founder and CEO

(Please feel free to add me to your LinkedIn network)

UPD: Editorial is out

Hey Codeforces (ﾉ◕ヮ◕)ﾉ*:･ﾟ✧

My team and I are happy to invite you to participate in Codeforces Round 878 (Div. 3). The round will take place on Jun/06/2023 17:35 (Moscow time). You will be offered 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.

You will be given 8 problems and 2 hours and 15 minutes to solve them. One of the problems in this round is interactive. Don't forget to read the guide on interactive problems.

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: diskoteka, pavlekn, playerr17, isosto.

We would like to thank:

1. Aris for coordinating the round

2. MikeMirzayanov for great Polygon and Codeforces platforms

3. step_by_step for red testing

4. Awesome3.14, I.Gleb, vladmart, dmkz, geospiza, phattd, fishy15 for yellow testing

5. KDZHR, D34D1NS1D3, JeffreyLC, NintsiChkhaidze, nickbelov, kamishogun, tolbi for purple testing

6. KoT_OsKaR, Gornak40, Serik2003, Nahian9696, Rudro25, ayhan23, Lyrically for blue testing

7. TkachDan for cyan testing

8. MODDI for green testing

9. midsho for grey testing

We wish you all good luck and a high rating!

UPD: Editorial published

Hi, Codeforces!

I welcome everyone to participate in Codeforces Round 877 (Div. 2), which will start on Jun/04/2023 17:45 (Moscow time).

The round will be rated for participants of Division 2 with a rating lower than 2100. Division 1 participants can participate unofficially in the round.

You will be given 6 problems and 2 hours to solve them. One of the problems will be interactive, so please read this guide if you are not familiar with interactive problems.

The score distribution will be 500 — 1000 — 1250 — 1750 — 2250 — 3000.

All problems were created and prepared by me.

I would like to thank:

• ScarletS and KAN for coordinating the round
• Alexdat2000 for translating statements to Russian
• AggravatedCow, ak2006, akifpatel, Awesome3.14, BucketPotato, dbaumg, Dominater069, EnDeRBeaT, errorgorn, fishy15, jampm, nickbelov, maomao90, Nahian9696, nyaruhodo, Olympia, phattd, prvocislo, PurpleCrayon, satyam343 for testing the round
• and of course, MikeMirzayanov, for the Codeforces and Polygon platforms

Good luck to all the participants!

Update: Editorial is available

Winners:

1. EmeraldBlock

2. dog_of_Nesraychan

3. tofudra

4. lmqzzz

5. LLyw6

Unofficial winners:

1. arvindf232

2. Vercingetorix

3. Geothermal

4. tabr

5. maspy

Hello, Codeforces!

I invite you to participate in Codeforces Round 876 (Div. 2), which will be held on Jun/03/2023 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 be given 5 problems and 2 hours to solve them. I recommend you to read all problems. One of the problems will be interactive, so please read guide for interactive problems before the contest.

All problems are authored by me.

I would like to thank:

• Renatyss for helping with preparation and discussing the problems.
• IgorI for great round coordination.
• bashkort, daubi, Ormlis, satyam343, maomao90, Dominater069, Umi, Kirill020708, asafiul, iliya_mon, sdyakonov, tolbi, Asgat, AquaMoon for testing the round and providing useful feedback.
• MikeMirzayanov for Codeforces and Polygon platforms.

Score distribution: 500 — 1000 — 1500 — 2250 — 2750.

Good luck to all participants!

Editorial has been published.

Winners:

1. arvindf734
2. caubetraidatmarvin
3. AmazingTalker_Frank
4. Perfectt
5. 1437vszombies

Unofficial winners:

1. Geothermal
2. Rubikun
3. Roundgod
4. neal
5. A_G

First-to-solve:

• A. M_bolshakov — 0:01.
• B. Never-Ever — 0:05.
• C. SSRS_ — 0:10.
• D. BucketPotato — 0:18.
• E. BeyondHeaven — 0:22.

Hello, Codeforces! Or, as we like to say in Romania: Sus Sus Sus, ca la Strehaia tată!

I am glad to finally invite you to participate in Codeforces Round 875 (Div. 1) and Codeforces Round 875 (Div. 2), which will start on 28.05.2023 17:35 (Московское время). In both divisions, you will be given 6 problems and 2 hours and 30 minutes to solve them.

The problems were authored and prepared by Andrei_ierdnA, Doru, Gheal, IacobTudor, LucaLucaM, RedstoneGamer22, SlavicG, Sochu, alecs, andrei_boaca, anpaio, lucaperju, valeriu and me ( tibinyte ).

I would like to thank:

• errorgorn, for his wonderful coordination.

• irkstepanov for further help with logistics of organization.

• Alexdat2000 for russian translation.

• alin_gb18, rsj, dario2994
  jampm, Psychotic_D, prvocislo
  cristi_tanase, atodo, BucketPotato
  Moolamp, magnus.hegdahl, Gary2005
  Geanina_the_Great, 555, PurpleCrayon
  Um_nik, gamegame, conqueror_of_tourist, penguinhacker, AlexLorintz, lucri, _Vanilla_, Vladithur, status_coding, Luci_badea1000, bycicle, myvaluska for testing the round and providing useful feedback.

• freak93 for no morning refreshment.

• MikeMirzayanov for great platforms, codeforces and polygon!

Scoring Distribution

• div 2: $$$500-750-1250-1750-2500-3000$$$
  

• div 1: $$$500-1000-1750-2250-3000-3500$$$

The editorial has been published here!

And here are our winners!