Hi Codeforces!

I am pleased to invite you to Adhocforces, Mathforces Codeforces Round #832 (Div. 2), which will take place on Friday, Nov 4, 2022 at 14:35 UTC. You will be given 5 problems and 2 hours to solve them.

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.

All problems in this round were prepared by me and CoderAnshu.

I would like to thank:

• antontrygubO_o for coordination of the round.
• ffao, Everule, Andreasyan, koderkushy, nor, AlperenT, the_hyp0cr1t3, Runtime-Terr0r, sp005, 18o3, KingRayuga, Scythe and sus for testing this round and giving really valuable feedback.
• MikeMirzayanov for the amazing Codeforces and Polygon platforms!
• You for participating.

The score distribution will be announced shortly before the round (or earlier).

Good luck and have fun! See you in the standings.

UPD 1:

Scoring distribution: 500 — 1000 — 1250 — 1750 — 2500

UPD 2:

I am flying to dhaka so will post editorials later.

UPD 3:

Congratulations to our winners!

Overall:

1. Um_nik
2. errorgorn
3. turmax
4. OtoriEmu
5. Vercingetorix

Div 2:

1. OtoriEmu
2. Nephren--Ruq--Insania
3. Silviasylvia
4. Gu_Zhou_Suo_Li_Weng
5. googolx

UPD 4: Editorial for A to C has been posted, will post D,E soon.

UPD 5: Editorial for D is posted.

UPD 6: Finally editorial for E is posted.

Halo, Codeforces! 🥰🥰🥰🥰

COMPFEST 14 is happy to invite you to participate in Codeforces Round 831 (Div. 1 + Div. 2) on Oct/29/2022 12:10 (Moscow time). Note the unusual time of the round. The round will be rated for everyone. You will be given 2 hours and 45 minutes to solve 9 problems.

The problems are written by NeoZap, Nyse, Pyqe, and steven.novaryo.

Scoring distribution: 500 — 1000 — 1500 — 1750 — 2000 — 2500 — 2750 — 3000 — 3500

We would like to thank:

• KAN for helping to host the round;
• errorgorn for the based coordination and help with the problem preparation;
• yz_ for helping with the problem preparation;
• MikeMirzayanov, geranazavr555 and KAN for writing the Russian translations;
• Aaeria, AMnu, dorijanlendvaj, eggag32, feecIe6418, fishy15, flamestorm, Gary2005, gisp_zjz, gyh20, MagentaCobra, mejiamejia, oleh1421, powergee101, ppavic, prabowo, Rewinding, tibinyte, tzc_wk, Wailydest for testing the contest and providing us very useful feedback;
• Universitas Indonesia, all the local committees, administrators, and managers of the whole COMPFEST event;
• rama_pang for drinking milk;
• MikeMirzayanov for the amazing Codeforces and Polygon platform!

COMPFEST itself is an annual event hosted by Universitas Indonesia. It is the largest student-run IT event in Indonesia and competitive programming contest is one of the competitions hosted.

We hope you will enjoy and have fun in the contest. Semoga beruntung dan selamat bersenang-senang!! 💪💪🔥🔥

Edit: round was delayed by 5 mins due to delays of onsite contest.

UPD: contest is over!

Congratulations to our winners!

1. jiangly
2. heno239
3. maroonrk
4. never_giveup
5. Isonan
6. ksun48
7. Um_nik
8. hank55663
9. ugly2333
10. Vercingetorix

We will try to post the editorials as soon as possible. Please stay tuned!

UPD 2 : Editorial

We are very sorry for the late editorial. We did not anticipate the workload of maintaining an onsite contest, especially since this is the first onsite contest held by our university in three years. We will use this experience to learn and improve our preparation next time.

Finally, we are delighted that the contest ran very well and that many of the contestants are enjoying the contest.

See you next year! 🥰🥰

Hello, Codeforces!

I am happy to invite you to my Codeforces Round 830 (Div. 2) which will be held at Oct/23/2022 13:05 (Moscow time). The round will be rated for all the participants with rating strictly less than 2100 before Oct/23/2022 10:50 (Moscow time).

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

• Coordinator Artyom123 for excellent communication and help with preparation.
• Testers gisp_zjz, Pointy, aaaaawa, feecIe6418, nnv-nick, xiaoziya, Ormlis, huangzirui, Chenyu_Qiu, triple__a, gyh20, low_, voventa, tibinyte, Mr.Robot_28, Qingyu, RUSH_D_CAT, physics0523, Lucina, Rhodoks, Tekor, Milesian, Kalashnikov, Lokeo, mejiamejia, TomiokapEace, Chenyu_Qiu, AquaMoon, MagicalFlower for high-quality testing and valuable advices.
• As well as the testers who tested the CheReKOSH Team Olympiad — it was from the problems of this Olympiad that the round was composed: orz, DIvanCode, CAMOBAP31.
• MikeMirzayanov for amazing Codeforces and Polygon platforms.

During the round you will need to solve 5 problems, some of which have subtasks. You will have 2 hours to solve them.

Score distribution will be announced shortly before the round.

We wish you good luck and high rating!

UPD: Score distribution: $$$750-750-(1000-1000)-(1250-1250)-3000$$$

UPD: Editorial

Hi everybody,

This Sunday there will be a XX Moscow Team Olympiad, high school students competition based in Moscow that is an elimination contest for All-Russian Team Olympiad. This contest is prepared by Moscow Olympiad Scientific Committee that you may know by Moscow Open 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, 707, 727, 751, 775, 802).

The round will be held at Oct/23/2022 10:50 (Moscow time) and will last for 2 hours. Note the unusual time of the round. Each division will have 6 problems. The round will be held according to the Codeforces rules and will be rated for both divisions.

Problems of this competition were prepared by Tikhon228, teraqqq, Ormlis, sevlll777, Artyom123, vaaven, Mangooste, Siberian, Alexdat2000, TeaTime, Ziware guided by Tikhon228, grphil and Helen Andreeva.

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

Also thanks to KLPP and TheOneYouWant for providing and preparation an additional problems that helped to create (I hope) a balanced problem set for the round.

Please note that the ratings will not be recalculated until Codeforces Round 830 (Div. 2), and system testing may be delayed until the end of Codeforces Round 830 (Div. 2).

Good luck everybody!

UPD1: The round was postponed by 15 minutes. Please note the new start time is Oct/23/2022 10:50 (Moscow time).

UPD2: Great thanks to the testers: Um_nik, dorijanlendvaj, errorgorn, vertig1, Makcum888, iakovlev.zakhar, Kon567889, I_love_geom, golikovnik, mejiamejia, Aleks5d, ak2006, jampm, IgorI! As well as the teams testing the main Olympiad: Elderly Passion Fruit (Siberian, alexxela12345, talant) and (maximrufed, omega_alpha, All1gator).

UPD3: Scoring distribution:

Div.2: 500 — 1000 — (750 — 750) — 1250 — 2000 — 2250

Div.1: (500 — 500) — 750 — 1750 — 2000 — 2500 — 3000

UPD4: Winners!

Div. 1:

1. jiangly
2. Rebelz
3. heno239
4. Radewoosh
5. LJC00118

Div. 2:

1. kzyKT
2. Vitinha
3. qtpk
4. Sugar0612
5. bdl

UPD5: Editorial

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• Register through the @toncontests_bot.

Hello Codeforces!

On Oct/20/2022 17:35 (Moscow time) Educational Codeforces Round 138 (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, 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!

UPD: Editorial is out

Hello Codeforces!

On Oct/17/2022 17:35 (Moscow time) Educational Codeforces Round 137 (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 Ivan BledDest Androsov, Alex fcspartakm Frolov and me. Also huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

The round is based on the Qualification stage of the Southern and Volga Russian Regional Contest. Thus, we kindly ask its participants to avoid participating in the round.

Good luck to all the participants!

UPD: Editorial is out

Hello! Codeforces Round 828 (Div. 3) will start at Oct/16/2022 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.

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.

Thanks to MikeMirzayanov for the platform, help with ideas for problems and for coordination of my work, pashka for help with ideas for problems and for coordination of my work. Problems have been created and written by MikeMirzayanov, 74TrAkToR and pashka.

We would like to thank: Gornak40, meowcneil, Vladosiya, senjougaharin, efimovpaul, powergee101, tanus_era for testing the contest and valuable feedback. List of testers will be updated.

Good luck!

UPD: Editorial

Hello Codeforces!

On Oct/15/2022 17:35 (Moscow time) we will host Codeforces Global Round 23.

It is the fifth round of a 2022 series of Codeforces Global Rounds. The rounds are open and rated for everybody.

The prizes for this round:

• 30 best participants get a t-shirt.
• 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.

The prizes for the 6-round series in 2022:

• In each round top-100 participants get points according to the table.
• The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
• The best 20 participants over all series get sweatshirts and place certificates.

Thanks to XTX, which in 2022 supported the global rounds initiative!

The problems were written and prepared by AmirrzwM, MohammadParsaElahimanesh and napstablook, AquaMoon, Cirno_9baka, mejiamejia, ChthollyNotaSeniorious, SSerxhs, TomiokapEace, SomethingNew, pakhomovee, rembocoder, SirShokoladina.

We would also like to thank:

• 74TrAkToR, for coordinating and helping a lot to make this round happen (and rejecting all of my problems).
• er888kh and Mp007mp for giving ideas for some problems.
• Our testers for testing and providing helpful feedbacks: er888kh, sinamhdv, SoheilE, DeadlyCritic, egfhdbfweryg123, gamegame, Kostroma, Endagorion, AndreySergunin, MELNIKOFF_OLEG, zemen, iwalainz, halin.george, -skyline-, mejiamejia, triple__a, TomiokapEace, SomethingNew, efimovpaul, Rhodoks, meowcneil, plagues, Milesian, blobugh, SSerxhs, apeiya, E404_Not_Found, RUSH_D_CAT, willy108, _Veritas, oolimry, aaaaawa and Ynoi.
• MikeMirzayanov for creating great platforms Codeforces and Polygon.

Round Information:

• Duration: 2 hours and 15 minutes
• Number of problems: 7 problems and 1 sub task
• Score distribution: 500-1000-1000-1500-(2000+1750)-2500-3500
• There is an interactive problem, so please see the guide of interactive problems if you are not familiar with it.

We have tried our best to write clear problem statements and make strong pretests and we are looking forward to your participation!

UPD: Editorial

Hello Codeforces!

mesanu, flamestorm, MikeMirzayanov and I are glad to invite you to Codeforces Round 827 (Div. 4)! It starts on Oct/13/2022 17:35 (Moscow time).

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 would like to thank:

• pashka, keta_tsimakuridze, Gheal, AlperenT, KrowSavcik, Sho, badlad, qwexd, Phantom_Performer, haochenkang, _Vanilla_, sandry24, jampm, tibinyte for testing and great feedback!

• TimDee for helping with russian translations!

• badlad for helping with a problem!

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

GLHF!

UPD: Editorial