This weekend, on Nov/24/2019 11:05 (Moscow time) we will hold Codeforces Round 602. It is based on problems of Technocup 2020 Elimination Round 3 that will be held at the same time.

Technocup is a major olympiad for Russian-speaking high-school students, so if you fit into this category, please register at Technocup 2020 website and take part in Technocup 2020 - Elimination Round 3.

Problem authors are me, nocriz, BledDest, adedalic and MikeMirzayanov. Many thanks to the testers: KAN, Supermagzzz, Stepavly, AdvancerMan and unreal.eugene!

Div. 1 and Div.2 editions are open and rated for everyone. As usual, the statements will be provided in English and in Russian. Register and enjoy the contests!

Have fun!

Scoring distribution:

Technocup: 500 1000 1250 (500+1500) 2500 (1000+2000) 3250

D1: 500 (500+750) 1500 (1000+1000) 2250 2500

D2: 500 1000 1250 (500+1500) 2500 (1000+2000)

UPD: Div1 Top5

1.sunset

2.tourist

3.WZYYN

4.jqdai0815

5.djq_cpp

And congratulations for djq_cpp to be the youngest Legendary GrandMaster in the age of 14!

Div2 Top5

1.funtik

2.PureWhite

3.nehnait

4.Fuyuki

5.rama_pang

And also the Editorial is out.

Starting from the version 1.3.1 of Codeforces Watcher, users can see latest Blog Posts in Recent Actions tab. It's already downloadable in Google Play.

Last few weeks BOGDAN_ spent by educating himself about multithreading and coroutines, which aren't easiest things in the universe ;) Thanks to his learnings, we've migrated Codeforces Watcher to Coroutines and it looks just great. You can see one of examples of confluence between Redux and Couroutines in AppMiddleware.kt.

By the way, Codeforces Watcher in an open-source project, so you are always welcome to check it out and learn new things or make suggestion on improvements. Stars won't hurt too, of course ;)

Hello! VKOSHP 2019 will begin on November 29, so we, like last year, decided to collect information on team ratings.

Here it is: https://standing.pythonanywhere.com/vkoshp/

Attention, changes to the table do not occur instantly. If you have any problems or you find a mistake, you can write in the comments or in PM @ismagilovcode.

And here are the teams that have good chances to become medalists this year:

Team	City	Participant 1	Participant 2	Participant 3	Rating
Power of Three	СПб	Ефремов Андрей receed	Гайнуллин Ильдар 300iq	Одинцов Андрей forestryks	8033
Mex Foundation	Москва	Лифарь Егор Egor.Lifar	Савкин Семён cookiedoth	Шеховцов Александр Jatana	7542
Graneli	Тбилиси	Birkadze Nika saba2000	Toloraia Teimuraz Temotoloraia	Basadzishvili Archil achi_basadzishvili	7255
а)	Москва	Ушаков Фёдор ----------	Федосеев Тимофей fedoseev.timofey	Пискалов Дмитрий TheWayISteppedOutTheCar	7189
Ого! Кажетсья это $#@!	Москва	Логинов Игорь IgorI	Шуклин Максим xoxo	Садовничий Антон sadovan	7092
Преимущественно овощи	Казань	Миннахметов Булат Minnakhmetov	Харисов Булат Nutella3000	Исмагилов Азат ismagilov.code	6912
Codewinter Genius	СПб	Харгелия Сергей UnstoppableChillMachine	Волков Иван Volkov_Ivan	Павленко Даниил D.Pavlenko	6838
Без названия	Гомель + Мозырь	Костяной Андрей VEGAnn	Харрасов Антон ne4eHbKa	Мищенко Андрей andrew	6752
Трави бобров спасай деревья	Москва	Фролов Константин fake123	Скворцов Юрий iura	Усачев Данила usachevd0	6716
Polit01-Nazik_number_one	Кременчуг	Мельник София Sonechko	Куц Андрей Jajceslav	Фомюк Артём impermanence	6684
БКШ	Челябинск	Будников Михаил Mlxa	Клищ Данил DanShaders	Шиляева Екатерина AlFlen	6644
Три кота (два кота и одна кошечка)	Екатеринбург	Лахтин Иван ialakhtin	Михайлов Виктор Catmoonlight	Гладченко Алиса AliceG	6598
Jigglypuff	Ереван	Андреасян Самвел Andreasyan	Абелян Александр enoone	Халатян Араи Arayi	6585
три гендера на троих	Москва	Радионова Мария Feechka_	Донской Станислав Stasana	Карпышев Сергей NekoKarp	6583
Пожилая Маракуйя	Москва	Маркелов Игорь Siberian	Пустовалов Юрий talant	Некрасов Александр alexxela12345	6459

Hello Codeforces!

I am glad to invite you to Codeforces Round #601, which will take place on Nov/19/2019 17:35 (Moscow time). The round will be rated for both divisions.

All problems in this round were created and prepared by a team of all-Vietnamese setters: MofK, I_love_tigersugar, UncleGrandpa, ngkan. This is the first Vietnamese Div1 round. We tried to make both the problems and the statements interesting and hope that you will enjoy them!

There is an interactive problem in the round. You can read the guide for interactive problem here.

We would like to give a lot of thanks to:

• MikeMirzayanov for the amazing platforms Codeforces and Polygon.

• arsijo for excellent coordination and many valuable advice for the round.

• Our team of testers: MikeMirzayanov, KAN, tanphatls987, Kuroni, AomeII, ngfam, goodthingstaketime_._, dush1729, lannh2207, nhakhoa, Sumeet.Shirgure, BledDest, NatInTheHat, AlexPop28 for testing the round and give feedback about the problems.

We wish you an exciting round!

UPD: The message from MikeMirzayanov. If the issue heavily affected you and you want the round to be UNRATED for you, you can fill the appeal form by the link: https://codeforces.com/userForm/f0458e24fa295 Please do not fill it just in case. Be honest, fill in only if the problem broke your participation in the contest. Mike.

UPD: There will be five problems for Division 1 and six problems for Division 2. The score distribution is as follows:

Division 1: 750 — (500 + 750) — 1500 — 1750 — 2500

Division 2: 500 — 1000 — 1500 — 1750 — (1000 + 1250) — 2750

UPD2: : Thanks for participating! Congratulations to the winners!!!

Div. 1: Top 5 are also the only 5 contestant managed to solve all problems!

1. Radewoosh

2. maroonrk

3. SkyDec

4. webmaster

5. ecnerwala

Honorable mention: taeyeon_ss for solving problem E in just 31mins!

Div. 2:

1. MbahSA1937 (solved all problems!)

2. mintwhale (solved all problems!)

3. Nightmare05

4. Don_Quijote

5. mangojunior

UPD3:Editorial is out!

Hello, Codeforces!

I'm glad to invite you to Codeforces Round 600 (Div. 2), which will be held on Nov/16/2019 17:35 (Moscow time). It will be rated for all participants with rating below 2100. You will be given six problems and two hours to solve them. As usual, the score distribution will be announced shortly before the round.

The problems were invented and prepared by me. Huge thanks to:

• faremy for taking time to solve and give me precious feedback on most of the problems I have considered putting into my round throughout its whole creation (more than 6 months!)

• 300iq for coordinating the round and giving helpful advices

• MikeMirzayanov for great systems Polygon and Codeforces

• dorijanlendvaj, McDic, nvmdava, Kuroni, fedoseev.timofey, budalnik, _overrated_, aneesh2312, arthurconmy, Ifugao, sdssudhu, Savior-of-Cross, cfalas, teekteek and Ashishgup for testing

This is the first french round on Codeforces, I hope that everybody will enjoy it :) GL&HF to all!

UPD1: Scoring distrubtion is 500-1000-1500-1750-2250-2750

UPD2: Editorial is out

UPD3: Thanks for participating! Congratulations to the winners:

Div.1 (unofficial) participants

1. Um_nik (solved all problems in 38 minutes!)
2. dreamoon_love_AA
3. mango_lassi
4. imeimi
5. cerberus97

Div.2 participants

1. Son
2. root_power_6
3. Do-Kwon
4. AlineSH
5. Hezx

First solve

• A. teapotd (2 minutes)
• B. nitrousoxide (7 minutes)
• C. saketh (4 minutes)
• D. Marisa (8 minutes)
• E. tfg (14 minutes)
• F. Deemo (30 minutes)

Hello Codeforces!

On Nov/13/2019 17:35 (Moscow time) Educational Codeforces Round 76 (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 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:

Attention Codeforces!

Calling on all tech disruptors, data specialists and computer science pioneers.
We are offering fully-funded international scholarships for exceptional tech specialists from around the world. Accelerate your career by becoming an industry expert capable of making key data-driven decisions that add value and drive innovation within tech industries.

Harbour.Space University has partnered with SCG, a leading business conglomerate in the ASEAN region, to offer exceptional tech specialists the opportunity to work and study in two of the most dynamic and vibrant cities in the world. Join our progressive two-year program based in Bangkok, with 6 of the 24 months in Barcelona, to develop the international mindset needed to accelerate your career and redefine how data drives the businesses of the future.

Tuition fee:

2 years | €45,800

Education:

3 hours of study per day | 15h per week

Work Experience:

4 hours of internship per day at SCG | 20h per week

Living Allowance:

€16,800 euros | €700 per month living allowance

Congratulations to the winners:

Congratulations to the best hackers:

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

UPD: Editorial is out

Hello, Codeforces!

I and cannor147, as students of ITMO University, joined the Codeforces team in June. From June to October, we mainly dealt with the development of the Polygon platform. In this post, we would like to present to you a list of what we have done during this time. This list does not include minor bug fixes or any improvements that are invisible to users.

PIN codes for problems and contests

Sometimes very important contests and problems are being developed in Polygon. In such cases, a leader of the jury may be worried about data leaking. For example, it can be so because of the weak password of another member of the jury. PIN code is an additional factor of confirmation the access for the problem or contest and it can be set up only by the owner. It is assumed that the PIN code will be sent in another secure way.

There is a link Create Pin for the owners in the contest interface:

If a contest or a problem has the PIN code, you need to type it before continuing.

You can manage the PIN code of the problem in the tab Manage Access in the problem interface. The owner can create the PIN code or copy the PIN code from a contest that contains the problem.

If you use Polygon API, there is a way to send requests for working with problems or contests, that have the PIN code. You have to provide a new additional parameter “pin” in your requests.

Groups of contests

Polygon grows up and the number of contests in Polygon grows up too. Sometimes you want to group some contests. For example, it seems convenient to group contests from the same programming workshop. Now in Polygon you can group some contests for faster management of the access rights for them.

I'm sadly announcing that a2oj.com (A2 Online Judge) will be retiring by end of 2019, I'll shut it down at midnight on New Year's Eve. It was something I took care of for about 10 years.

I'm really sorry, but I prefer not to explain my reasons, so please don't ask me why I'm doing this, it was hard enough for me to make this decision, and also please don't try to convince me to change my mind.

I'd like to say thank you to everyone who used it, and please accept my sincere apologies for shutting it down.

If you have something good to say about A2OJ (how you used it or how it helped you in any way), I'd love to read that, please send it to the following email (or in a comment here): [email protected]

Also please feel free to take a copy of any data you can access, and if you need some data in a specific format, please send your request to the following email: [email protected] (if the data isn't public, make sure to send from your registered and verified email which can access this data). I'll do my best to fulfill all requests.

Please only use the above email, because soon I'll be deactivating my personal Facebook account again, I'll also deactivate A2 Online Judge.

Edit 1: I'll keep a static version of all Ladders & Categories.

Edit 2: Here's how I generated the ladders, in case if anyone wants to implement it: https://codeforces.com/blog/entry/47442

Edit 3: A2 Online Judge is shut down now, and a static version of all ladders and categories is available. And here are some final numbers for the record:

Database numbers:

• 24,012,628 total number of database rows.
• 99,242 registered users.
• 33,133 created contests.
• 1,581,430 submissions collected from other online judges.
• 937,658 different source codes stored in the database.
• 261,733 compiled and executed source codes (in 54 different languages).
• 6,144,545 user solved problem entries (detected that a user solved a problem).
• 377,580 problems added to contests.

Google Analytics numbers:

• 30,265,387 page views.
• 5,252,045 sessions.
• 1,157,668 users.

Top 10 countries from Google Analytics:

1. India
2. Egypt
3. Brazil
4. United States
5. Bangladesh
6. Peru
7. Jordan
8. Syria
9. Colombia
10. Bolivia