Hello Codeforces!

flamestorm, MikeMirzayanov and I want to invite you to Codeforces Round 898 (Div. 4).

It starts on 21.09.2023 17:35 (Московское время).

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 behaviour. 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.

Many thanks to the testers: Gheal, Phantom_Performer, KrowSavcik, haochenkang, sandry24, BucketPotato, Vladosiya, NintsiChkhaidze, erekle, Dominater069, MADE_IN_HEAVEN, Qualified.

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

Good Luck!

UPD: Editorial is out!

Привет, Codeforces!

Мы с SomethingNew рады пригласить вас на CodeTON Round 6 (Div. 1 + Div. 2, Rated, Prizes!), который пройдёт в 18.09.2023 17:35 (Московское время). У вас будет 2 часа 15 минут на решение 8 задач. Раунд будет рейтинговым для всех.

Мы хотим выразить благодарность:

• RedMachine-74 за координацию раунда.
• isaf27, ugly2333, JianfengZhu, Little09, bashkort, Kieray, fishy15, Vladithur, Dart-Xeyter, pakhomovee, makrav, meowcneil, 127.0.0.1, nanani, nnv-nick, SomethingDifferent, vl342, shiv_codegen, M1lkas, allmath, sdyakonov за тестирование раунда и полезный фидбэк.
• MikeMirzayanov за системы Codeforces и Polygon.

Разбалловка:

500 — 750 — 1500 — 1750 — 2750 — 3250 — 3250 — 4000

Мы надеемся, что наши задачи будут интересными для вас!

Разбор

Поздравляем победителей!

1. orzdevinwang
2. cnnfls_csy
3. jiangly
4. emptyhope
5. maspy
6. tourist
7. AoLiGei
8. Um_nik
9. noimi
10. Geothermal

Информация от спонсора этого раунда:

Hello, Codeforces!

We, the TON Foundation team, are pleased to support CodeTON Round 6.

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 6 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 6 and hope you enjoy the contest!

Привет, Codeforces! 🤯

green_gold_dog, ace5, bashkort и я salyg1n рады пригласить вас принять участие в Codeforces Round 897 (Div. 2), который состоится в понедельник, 11 сентября 2023 г. в 17:35.

Этот раунд будет рейтинговым для участников, чей рейтинг ниже 2100. Участники с более высоким рейтингом могут принять участие вне конкурса.

Вам будет предложено 6 задач и 2 часа на их решение. Советуем прочитать все задачи. В раунде могут встретиться интерактивные задачи. Рекомендуем прочитать этот пост.

Мы хотим поблагодарить:

• Aleks5d за координацию раунда и улучшение одной из задач. 🤓

• allvik66, Nutella3000, arbuzick, alegsandyr, maomao90, FairyWinx, zwezdinv, valerikk, danya111, EJIC_B_KEDAX, dushenkov, fishy15, makrav, pakhomovee, alexashkins, 555105, asafiul, Ivan_len, ArtAlex, Undying, JustNik77, Pavarishko и run2wice за тестирование раунда и ценную обратную связь. 🙏 orz

• ryskmax за единственное синее тестирование раунда и ценную обратную связь. 🐳

• DimaTomsk и ilyakrasnovv за просмотр некоторых задач и ценную обратную связь. 🤠

• stepanov.aa за то, что он так и не протестировал раунд. 🦥 За что ты так :(

• Авторов задачи 5. Overtaking с IOI 2023 за то, что bashkort взял золотую медаль. 🥇 Иду по снегу, он хрустит

• MikeMirzayanov и geranazavr555 за прекрасные платформы codeforces и polygon. 🦖 Большое спасибо! :D

Мы надеемся, что вам понравятся наши задачи! Удачи!

UPD. Разбалловка: $$$500 - 1000 - 1250 - 2000 - (2000 + 1000) - 4000$$$.

UPD2. Поздравляем победителей!

Div. 2

1. candidatecandidatemaster

2. Coreopsis

3. iFFT

4. Dorothy__

5. wk______tzc

Div. 1

1. Golovanov399

2. Geothermal

3. arvindf232

4. Rubikun

5. Vercingetorix

UPD3. Разбор.

Hello, Codeforces! & Happy Chinese Teachers' Day!

We (OICon Team) are so excited to invite you to take part in OICon Round 1 (Codeforces Round 896 (Div. 1) and Codeforces Round 896 (Div. 2)) which will start on 10.09.2023 17:05 (Московское время). You will be given 6 problems and 2.5 hours to solve them in both divisions.

• Please notice the unusual starting time!
• One of the problems has two versions but their statement are not exactly the same, which means that you can't pass the easy version using the code of the hard version. However, you can only make hacks when you pass both versions.
• There will be $$$0$$$ interactive problem in each division so you needn't read the guide for interactive problems.
• Score distribution:
  • Div. 1: $$$500-(500+750)-1000-1750-2500-3000$$$
  • Div. 2: $$$500-750-1250-(1250+1500)-2500-3250$$$

The problems were authored and prepared by Error_Yuan, duck_pear, programpiggy and me.

We would like to thank:

• Artyom123 for his long-term & high-quality coordination 😊😊😊
• Again, Artyom123 for the Russian translation 👍👍👍
• dqstz, BreakPlus, ZYPRESSEN for providing a few rejected problems 😭😭😭
• Um_nik, gyh20, MagicalFlower, Sugar_fan for Legendary GrandMaster testing 👽👽👽
• sansen, Kubic, Alex_Wei for International GrandMaster testing 😎😎😎
• rui_er, ling_luo, swiftc, SeeleVollerei, N_z__, __builtin_gjr for GrandMaster testing 🧐🧐🧐
• HappyIvan, Azuma_Seren, User_Carrot, Wilson_Inversion, chen_03, Valters07, EternalJourney, Kieray for Master testing 😯😯😯
• guoziyang, NoCommander, Alan_dong, small_peter for Candidate Master testing 🤔🤔🤔
• Coffee_zzz, fAKezjf, purplevine, Black_Fate for Expert testing 😃😃😃
• mikcf, A.I.skeleton_ for Specialist testing 🙂🙂🙂
• wz20201136 for the only Newbie testing 👀👀👀
• ChatGPT for getting 0 point in both divisions 🤡👈🤣
• And, You, for participating and getting positive delta 😘😘😘
• Last but not least, MikeMirzayanov for great Polygon and Codeforces platforms 🎅🎅🎅

Good Luck & Have Fun!

UPD1. Editorial is out.

UPD2. Contest is over! Congratulations to the winners!

Привет Codeforces! В 07.09.2023 17:35 (Московское время) начнётся Codeforces Round 895 (Div. 3). В этом раунде будет 7 задач, которые подобраны по сложности так, чтобы составить интересное соревнование для участников с рейтингами до 1600. Однако все желающие, чей рейтинг 1600 и выше могут зарегистрироваться на раунд вне конкурса.

Раунд пройдет по правилам образовательных раундов. Таким образом, во время раунда задачи будут тестироваться на предварительных тестах, а после раунда будет 12-ти часовая фаза открытых взломов. Мы постарались сделать приличные тесты — так же как и вы, мы будем расстроены, если у многих будут падать решения после окончания контеста.

Вам будет предложено 7 задач и 2 часа 15 минут на их решение.

Штраф за неверную попытку в этом раунде будет равняться 10 минутам.

Напоминаем, что в таблицу официальных результатов попадут только достоверные участники третьего дивизиона. Как написано по ссылке — это вынужденная мера для борьбы с неспортивным поведением. Для квалификации в качестве достоверного участника третьего дивизиона надо:

• принять участие не менее чем в пяти рейтинговых раундах (и решить в каждом из них хотя бы одну задачу)
• не иметь в рейтинге точку 1900 или выше.

Независимо от того являетесь вы достоверными участниками третьего дивизиона или нет, если ваш рейтинг менее 1600, то раунд для вас будет рейтинговым.

Задачи были придуманы и подготовлены: Alexdat2000, FairyWinx, sevlll777, Vladosiya, и MikeMirzayanov.

Также большое спасибо:

1. Vladosiya за прекрасную координацию раунда, и помощь в подготовке и балансировке набора задач.
2. MikeMirzayanov за платформы Polygon и Codeforces.
3. Ormlis за чёрно-красное тестирование раунда.
4. zwezdinv, BledDest за красное тестирование раунда.
5. Sokol080808, diskoteka, Sweezy, vladmart, Kniaz, Temirlan, Riblji_Keksic, RedMachine-74, pavlekn за жёлтое тестирование раунда.
6. moonpieXXIV, gs20036, Kolychestiy за фиолетовое тестирование раунда.
7. martin0327, tnaito, no_mind, Pa_sha, JuicyGrape, ctraxxd, ezdp, FiniteMoves за синее тестирование раунда.
8. NerfThis, _SADIEM_, YudoTLE, sayed_4 за циановое тестирование раунда.

Всем удачи!

UPD: Разбор

Hello, Codeforces! 😍😍

We are happy to invite you to participate in COMPFEST 15 Preliminary Online Mirror (Unrated, ICPC Rules, Teams Preferred) on . COMPFEST is a national ICPC-style contest for university students in Indonesia.

The problems are written and prepared by ArvinCiu, asteriskzie, CyberSleeper, Edbert.H, FreeJinG, gansixeneh, KokiCoder, nandonathaniel, and Pyqe.

We would also like to thank:

• KAN for helping to host the mirror round;
• AMnu, (KerakTelor, Owmicron, ZeroScar), (tzaph_, Berted, Elben85), errorgorn, Drew_, and joelgun14 for testing the contest and providing us very useful feedback;
• Universitas Indonesia, all the local committees, administrators, and managers of the whole COMPFEST event;
• fushar for the Judgels platform used in the official contest; and finally
• MikeMirzayanov for the amazing Codeforces and Polygon platform!

The contest will last for 5 hours and consist of 13 problems. The statements will only be available in English. While it is preferred to participate in a team, individual participation is also allowed.

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. Good luck! 🔥🔥🔥🔥

UPD: Contest is over!

Congratulations for our first solvers!

• A: arvindf232
• B: maspy
• C: (Speed Star: noimi, SSRS_)
• D: (ITMO PTU: dimss, Kirkon, andreyDagger)
• E: Morphed
• F: (JoesSR fan club: red-stone, LXH-cat, NetSpeed1)
• G: (DELIAIR: sapphire15, tokusakurai, torisasami)
• H: (Hamood? Hamood!: qiuzx, njwrz, sjcsjcsjc)
• I: (absinthe: user202729, nvmdava, rama_pang)
• J: (Beyond Three Wolves: Omphalos, Kevin114514, Gellyfish)
• K: (致远星: AlternatingCurrent, PersistentLife, grass8sheep)
• L: (Team named after Elena Engurazova: otsekai, oversolver, Blinov_Artemii)
• M: hos.lyric

Editorial is available here!

Привет, Codeforces!

В 31.08.2023 17:35 (Московское время) состоится Educational Codeforces Round 154 (Rated for Div. 2).

Продолжается серия образовательных раундов в рамках инициативы Harbour.Space University! Подробности о сотрудничестве Harbour.Space University и Codeforces можно прочитать в посте.

Этот раунд будет рейтинговым для участников с рейтингом менее 2100. Соревнование будет проводиться по немного расширенным правилам ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением, равен 10 минутам. После окончания раунда будет период времени длительностью в 12 часов, в течение которого вы можете попробовать взломать абсолютно любое решение (в том числе свое). Причем исходный код будет предоставлен не только для чтения, но и для копирования.

Вам будет предложено 6 или 7 задач на 2 часа. Мы надеемся, что вам они покажутся интересными.

Задачи вместе со мной придумывали и готовили Адилбек adedalic Далабаев, Иван BledDest Андросов, Максим Neon Мещеряков и Роман Roms Глазов. Также большое спасибо Михаилу MikeMirzayanov Мирзаянову за системы Polygon и Codeforces.

Отдельное спасибо тестеру раунда stAngel за ценные советы и предложения!

Удачи в раунде! Успешных решений!

Также от наших друзей и партнёров из Harbour.Space есть сообщение для вас:

Harbour.Space University в партнерстве с Giga (Unicef) предлагают стипендию для получения степени магистра в сфере даталогии, а так же опыт работы.

Мы ищем различных кандидатов от junior до mid уровня:

Специалист по работе с данными:

• Хорошие знания в области машинного обучения
• Опыт работы с инструментами визуализации данных, такими как matplotlib, ggplot, d3.js., Tableau, которые помогают визуально кодировать данные
• Отличные коммуникативные навыки – невероятно важно описывать результаты технической и нетехнической аудитории
• Сильный опыт разработки программного обеспечения
• Практический опыт работы с инструментами обработки данных
• Способность решать проблемы
• Аналитический ум и отличное деловое чутье
• Высшее образование в области компьютерных наук, инженерии или смежной области приветствуется

Аналитик данных:

• Подготовка данных
• Анализ и изучение данных
• Знание статистики
• Анализ и визуализация данных
• Отчеты и панели индикаторов
• Общение и переписка
• Знание предметной области
• Ориентированность на решение

Все успешные кандидаты будут иметь право на получение стипендии со стопроцентной оплатой обучения (29 900 евро в год), предоставляемой нашими партнерами.

ОБЯЗАТЕЛЬСТВА КАНДИДАТА

Обучение: 3 часа в день

За год обучения вы завершите 15 модулей (длительность каждого 3 недели). Ежедневная учебная нагрузка составляет 3 часа, плюс домашнее задание, которое нужно выполнить в свободное время.

Работа: 4 часа в день

Погрузитесь в профессиональный мир во время обучения. Вы будете учиться у лучших и с первого дня сможете применять свои новые знания на практике.

ТРЕБОВАНИЯ

• Опыт работы в отрасли
• Международный опыт
• Стремление к обучению
• Устойчивое развитие ключевой момент для вас
• Желание работать на общественную организацию

UPD: Разбор опубликован

Hey, Codeforces!

Pinely is here! Just like every year, we are sponsoring the PTZ competitive programming camp. As a part of this, we have prepared a contest for the participants and invite everyone to join it on Codeforces.

Pinely Round 2 (Div. 1 + Div. 2) is scheduled to start on 30.08.2023 17:35 (Московское время).

During this round, you will have the opportunity to solve 9 problems within a time frame of 3 hours. The round will be rated for everyone.

The problems have been authored and prepared by the Pinely team: AndreySergunin, ch_egor, Endagorion, amethyst0, zeliboba, zemen along with our special friend Golovanov399.

We would like to express our special thanks to:

• WrongAnswerOnTest3, bkbtpout, PurpleCrayon, Silver_Fox, maomao90, qrewetka, Vladithur, nigus, jdurie, alwyn, dorijanlendvaj, OAleksa, ognjentesic, Kostroma, oursaco, tiger2005, SSerxhs, absi2011, EternalAlexander, EternalJourney, wh0816, Kieray, socpite for testing,

• irkstepanov and KAN for coordination

• MikeMirzayanov for the amazing Codeforces and Polygon platforms.

We sincerely hope that you enjoy our contest. Wishing you good luck and lots of fun!

UPD. Score distribution: $$$500$$$ — $$$750$$$ — $$$1000$$$ — $$$1250$$$ — $$$1750$$$ — $$$2500$$$ — $$$2750$$$ — $$$3500$$$ — $$$4000$$$.

P.S. If you are interested in working at Pinely, please visit our website: https://pinely.com/, send us an email at [email protected] or fill in the form here

Congratulations to the winners!

1. tourist
2. Radewoosh
3. QAQAutoMaton
4. jiangly
5. Ormlis

Editorial.

Hello everyone, we are happy to announce that the 2nd Universal Cup has started officially.

The Universal Cup is a non-profit organization dedicated to offering training resources for competitive programming teams. Our website is https://ucup.ac/ (in English and Chinese).

In the previous season, over 750 teams from more than 300 affiliations all over the world, registered and participated in a total of 22 stages, encompassing contests from Asia, Europe, and America.

With the permission of contest setters and without involving copyright disputes, the Universal Cup will hold mirror contests for some undisclosed competition sets. It is expected to hold at least 20 contests in this season. We will simulate the actual situation in the competition, executing the board freeze in the last hour. At the same time, we will provide an overall rating board, which will help the team to make a reasonable assessment of itself.

Over the past few weeks, the committee has worked hard to schedule stages and try to improve the competing experience for participants. We are very excited to share some information here as a head up:

• In the upcoming 2nd Universal Cup, starting from September 2nd, 2023, we have already scheduled 14 high-quality stages from Asia and Europe mainly. The current schedule can be viewed on the main page of our website https://ucup.ac/.

• There are also 4 stages (expected on October 7th, 14th, 21st, and December 9th) in confirming. The schedule in the second half will also be updated later.

• We have managed to upgrade our judging system on QOJ, and we will use it as the contest platform starting this season. To provide more flexibility, instead of 3 fixed time windows, teams now can choose to start to compete in one of the following 6 windows as they want:

  • 13:00 (UTC +8) on Saturday ~ 18:00 (UTC +8) on Saturday
  • 16:00 (UTC +8) on Saturday ~ 21:00 (UTC +8) on Saturday
  • 19:00 (UTC +8) on Saturday ~ 24:00 (UTC +8) on Saturday
  • 21:00 (UTC +8) on Saturday ~ 02:00 (UTC +8) on Sunday
  • 23:00 (UTC +8) on Saturday ~ 04:00 (UTC +8) on Sunday
  • 02:00 (UTC +8) on Sunday ~ 07:00 (UTC +8) on Sunday

• For teams that have already registered, if they have done at least 3 contests in the previous season, their account will be preserved and enrolled into the current season automatically. Otherwise, the same as new teams, please register following the instructions on Registration.

• The official website has been upgraded. You are able to view all information from the previous by simply choosing the corresponding season on the website.

The first contest will be the stage Qingdao on September 2nd, 2023. The contest source is The 2018 ACM-ICPC Asia Qingdao Regional Online Contest prepared by SUA Problem Setter Team. For a great number of Chinese teams, we believe this will be a good practice to prepare for the upcoming ICPC preliminary online contests in late September.

As well as many other future stages, this stage will be uploaded to Gym afterward. We are grateful to MikeMirzayanov for letting us advertise Universal Cup in Codeforces and providing the great platform Codeforces and Polygon to help prepare contests. We are also very thankful to all contest setters of stages for your support to the Universal Cup. If any setter would like to propose a stage, please feel free to contact us.

Universal Cup Committee:

• Jingbang chenjb Chen
• Yuhao jqdai0815 Du
• Lingyu jiangly Jiang
• Yaowei Sugar_fan Lyu
• Qingyu Qingyu Shi
• Yaohui quailty Zeng

(Sorted by lexicographical order of the last name)

Salam, Codeforces! $$$\color{white}{\text{ «Be attentive about your thought that becomes your behavior» «Be attentive about your behavior that becomes your speech» «Be attentive about your speech because it becomes your habit»«Be attentive about your habit because it becomes your personality»«Be attentive about your personality because it becomes your destiny» Said by: Imam Ali}}$$$

We're so excited to invite you to take part in our round Harbour.Space Scholarship Contest 2023-2024 (Div. 1 + Div. 2) which will start on Aug/26/2023 17:35 (Moscow time). The round will be rated and open for everyone.

The problems were prepared and authored by amenotiomoi, Dhruvil Psychotic_D Kakadiya, Han wuhudsm Jinlong, Amir Hossein Amir_Parsa Farhadi, Matthew chromate00 Roh, JohnVictor, ODT, ugly2333, EternalJourney, RiverHamster, MagicalFlower and AquaMoon.

We would like to thank :

• irkstepanov for coordinating the round;
• aaaaawa, BurnedChicken, p_b_p_b and Sugar_fan for LGM testing;
• hibye1217, alireza_kaviani, errorgorn, JianfengZhu, AmShZ, Crying, Huah, bthero, fengzhengwei and Ecrade_ for GM and IGM testing;
• Kieray, k1r1t0, Arpa, triple__a, blxst, leukocyte, ITO and NemanjaSo2005 for M and IM testing;
• tbank, TAIYANGFENG, callmepandey, Mkswll and uuku for CM testing;
• WrongAnswerOnTest3, KitasCraft, aayushdhankecha, Qualified, nanani, USACOW and tllwtg for Expert testing;
• Hex-willappear, Savani004, AkibAzmain, Visrut_, Banis and Harshil4442 for Specialist testing;
• strange-creator for the only Pupil testing;
• Valenz for the only Newbie testing;
• MikeMirzayanov for the great Codeforces and Polygon platforms;
• And at last but not least, You for participaing in the round!

You will be given $$$9$$$ problems and $$$3$$$ hours to solve!

Score Distribution:

$$$500-1000-1250-1500-2000-2500-3000-3500-4250$$$

UPD1 : Editorial is out.

UPD2 :

First Solve

Top Performers

GL & HF ;)

This round wouldn't have been possible without Harbour.Space University's support.

This contest is for all interested eligible programmers who want to start their bachelor and master studies in Barcelona, Spain or Bangkok, Thailand, and join ICPC team.

For the next academic year (2023/24), Harbour.Space University is recruiting a fascinating community of competitive programmers from the top prize-winners of international Olympiads to join one of several competitive programming teams at the university.

In the next few years, their goal is to continue winning SWERC and competing at a high level in the ICPC globally. Therefore they want to invest a serious amount of energy, resources, and talent into these activities.

That’s why you are invited on an exciting journey in the company of like-minded people, outstanding coaches, and ongoing partnership Harbour.Space University with Codeforces.

Over 100 educational rounds were already organized, so the time has come to test our joint efforts and reward the most diligent.

Here’s what you win if you place in the contest:

The monthly living allowance throughout the entire duration of studies may vary depending on the overall performance of the students as measured by their GPA, professional achievements and official ICPC competition results. As a guideline, it is in the range of 700-1500 EUR (it might be applied to the contestants who win 4th-10th places).

No application fee is required for any of the awards listed above.

Good luck, and may the code be with you!