Hello Codeforces!

On December 28, 17:05 MSK Educational Codeforces Round 35 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 Div. 2. It will be held on extented ACM ICPC rules. After the end of the contest you will have one day 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 prepared by Ivan BledDest Androsov, Vladimir vovuh Petrov, Alexey Perforator Ripinen and me.

Thanks Mike MikeMirzayanov Mirzayanov for great system Polygon!

Good luck to all participants!

We also have a message from our partners, Harbour.Space University:

Hello everyone!

Registration is open for our upcoming 1st Hello India x Russia Programming Bootcamp, with 20 teams signed up and counting, and we are looking forward to seeing you and your teammates in India this March!

More information

Register here

UPD: There will be 7 problems!

Congratulations to the winners:

Congratulations to the best hackers:

1761 successful hacks and 1237 unsuccessful hacks were made in total!

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

UPD2: Editorial is out

Codeforces Round #455 for Div 2 competitors will be held on December 27 at 19:35 MSK. As usual, Div 1 competitors can join out of competition.

The round will be rated.

This round is based on tasks for summer contest for interns algO(1). If you have seen the problems from that contest before, please don't participate in the round. The problems were prepared by Maxim Kalinin (slycelote), Alexander Milanin (Milanin), Ibragim Ismailov (ibra) and me (Nickolas).

The competitors will be given six problems and two hours to solve them. The scoring distribution will be 500-1000-1500-1750-2000-2500.

We hope you'll like the problems. Good luck!

UPD: thanks to HellKitsune, vintage_Vlad_Makeev, 300iq, Arpa and Livace for testing the problems!

UPD: The contest is over. Editorial can be found here.

Congratulations to winners!

Div. 2:

1. MegaOwIer
2. skuecrk
3. Vergara
4. Luqman
5. UoA_Kaori

Div. 1:

1. Benq
2. dotorya
3. uwi
4. I_love_Tanya_Romanova
5. ksun48

Hi all!

This weekend, at 14:05 UTC on December 23rd we will hold Codeforces Round 454. It is based on problems of Technocup 2018 Elimination Round 4 that will be held at the same time.

Technocup is a major olympiad for Russian-speaking high-school students, so if you fall into this category, please register at Technocup 2018 website and take part in the Elimination Round.

I would like to thank veschii_nevstrui, adamant and DPR-pavlin who authored and prepared problems for Technocup and ifsmirnov, Kostroma, winger, AlexFetisov, 300iq for testing the round.

Div. 1 and Div.2 editions are open and rated for everyone. Register and enjoy the contests!

Congratulations to the winners!

Technocup:

1. ---------

2. I_love_Palindromic_Tree

3. iakovlev.zakhar

4. IsmagilS

5. DCNick3

Div. 1:

1. jqdai0815

2. Radewoosh

3. Swistakk

4. Um_nik

5. consecutivelimit

Div. 2:

1. Kammola

2. ehnryx

3. LifeCracker

4. emoairx

5. laofudasuanbaofushehui

UPD: Editorial

Hello, Codeforces!

I want to test the system before the rated rounds based on Technocup stage, to be sure that everything works as expected.

I invite you to take part in Testing Round 14 (Unrated). It will start soon, on December, 22, 11:05:00 (UTC). It will be unofficial unrated round. The duration is 90 minutes.

Pretests are unusually weak to trigger more hack.

Thank you,
MikeMirzayanov

UPD: Thank you for participation. I didn't notice any bugs. It seems we are ready for new rounds!

Hello!

In this post I will talk about recent innovation in Codeforces.

It is noticed that many coaches used the opportunity to change the start of the training/rename it for personal purposes (to host group trainings). This leads to confusion and inconvenience for other members of the community.

To keep everything in order, we changed the rules for editing gym contests. Now a coach can change the name/start time/description of a gym if it is not public or the last update was made not later than a week ago. A week after editing a gym, it becomes the history of Codeforces and coaches lose an opportunity to make edits in it.

You cat ask "how do you give a training in a group, specifying the start time?" Now there is such a way!

To allow more convenient re-use of past trainings, as well as regular contests, it was possible to copy past training and regular competitions into a mashup. This can be done by clicking on the corresponding button in the right sidebar or directly in the form of mashup creation.

In the copied mashup all the submissions of participants of parent contest, the statements of the problems and other information are inherited. Thus, it is a convenient way to start a training in a group at a specific time (now participants will participate in an ordinary way, and not make a synchronous virtual start), giving it its own name.

Wish you successful trainings!

Hi everyone!

Missed me? I bet no! In either way, here goes another one round which I dared to spoil by my participation in problemsetting. Welcome to the world of extremely unoriginal problems, awkwardly long and boring statements and trifling jokes in anouncements.

This time round was prepared by Ildar Gainullin (300iq) and me (I'm ashamed to place link of such color here, you know who). We want to thank Vladislav Isenbaev (winger), Konstantin Semenov (zemen), Alexey Shmelev (ashmelev), Ivan Smirnov (ifsmirnov) and Alex Fetisov (AlexFetisov) for testing problems and help in preparation. Also special thanks goes to Nikolay Kalinin (KAN) for his help as coordinator and, of course, MikeMirzayanov for polygon and codeforces.

We hope that you will enjoy the problems, good luck and have fun!

UPD. Also thanks to akvasha for completing our problemset by his problem.

UPD 2. The contest is over, congratulations to winners!

Div. 1:

1. dotorya
2. Um_nik
3. Radewoosh
4. ainta
5. dreamoon_love_AA

Div. 2:

1. UoA_Kaori
2. noelnadal
3. mtw
4. Kroma
5. Yjsu

Here are editorials.

Hello again, Codeforces!

I'd like to invite you to Codeforces Round #452 (Div. 2). It'll be held on Sunday, December 17 at 09:35 MSK and as usual Div. 1 participants can join out of competition. Note that round starts in the unusual time!

The round is rated.

This round is held on the tasks of the second day of the municipal stage All-Russian Olympiad of Informatics 2017/2018 year in city Saratov. They were prepared by Olympiad center of programmers of Saratov SU. A convincing request to the participants of the municipal stage in Saratov to do not participate in this contest.

Great thanks to Nikolay Kalinin (KAN) and Grigory Reznikov (vintage_Vlad_Makeev) for helping me preparing the contest, to Mike Mirzayanov (MikeMirzayanov) for the great Codeforces and Polygon platform and to Alexey Ripinen (Perforator) for writing solutions.

You will be given six problems and two hours to solve them. The scoring distribution will be published soon. Good luck everyone!

UPD The scoring distribution 500-1000-1500-1750-2250-2500

UPD: The system testing is starting now, but upsolving, virtual participation and viewing solutions and tests will be disabled till the end of the olympiad in Saratov (around 2-3 hours from now). Hope for your understanding. Editorial will be posted after the olympiad as well.

UPD Congratulations to the winners!

1. Spyt

2. taew

3. Fop_zzZ

4. kabuszki

5. Join_VNOI_Discord

UPD Editorial

Hello, Codeforces!

I'd like to invite you to Codeforces Round #451 (Div. 2). It'll be held on Saturday, December 16 at 14:35 MSK and as usual Div. 1 participants can join out of competition. Note that round starts in the unusual time!

The round is rated.

This round is held on the tasks of the municipal stage All-Russian Olympiad of Informatics 2017/2018 year in city Saratov. They were prepared by Olympiad center of programmers of Saratov SU. A convincing request to the participants of the municipal stage in Saratov to do not participate in this contest.

Great thanks to Grigory Reznikov (vintage_Vlad_Makeev) and Nikolay Kalinin (KAN) for helping me preparing the contest, to Mike Mirzayanov (MikeMirzayanov) for the great Codeforces and Polygon platform and to Alexey Ripinen (Perforator) and Roman Glazov (Roms) for writing solutions.

You will be given six problems and two hours to solve them. The scoring distribution 500-750-1500-1750-2000-2500. Good luck everyone!

UPD Editorial

UPD2 Congratulations to the winners!

1. Namys

2. MSeashell

3. zhouyidong

4. ITMO.MansNotHot9

5. meoconn