I apologize to the participants of the round. It happened that I accidentally had run improper script and it rebooted the judging machines. It is very insulting, because most problems were proposed by me and I hoped to host an interesting competition for you. A lot of effort was spent on preparation. Apparently, the mistake of just such a human character happened for the first time. I really hope not to repeat it in the future.

MikeMirzayanov

Want problems? We have some!

Codeforces Round 434 will start on September 17 (Sunday), 13:05 (UTC). It will be based on Technocup 2018 Elimination Round 1. So, if you are a Russian-speaking high-school student, please take part in the Technocup 2018.

Many thanks to KAN, vovuh, Neon, ifsmirnov, irkstepanov and WHITE2302 for their help in round preparation. Some problem ideas are mine.

I hope you will like problems. There will be 6 problems in div. 2 and 5 problems in div. 1.

Wish you good luck and bugless code.

MemSQL is excited to announce Start[c]UP 3.0 – the third iteration of the programming competition hosted by Codeforces with an onsite at MemSQL HQ in San Francisco, California.

Start[c]UP 3.0 consists of two rounds. Round 1 is online and takes place on September 16th at 10:35 AM PST. Round 1 follows regular Codeforces rules and consists of at least 5 problems. For this round, the complexity of the problems will be comparable to a regular Codeforces round. There are no eligibility restrictions to participate in the round. The round will be 2.5 hours long, and will be rated.

Round 2 takes place on September 30th at 10:30 AM PST and uses regular Codeforces rules. The complexity of the problems is higher than a regular Codeforces round, the round will be 3 hours long, and will be rated. Only people who finished in the top 500 in Round 1 can participate. The top 100 in round 2 will receive a Start[c]UP 3.0 T-shirt.

For Silicon Valley residents, MemSQL will be hosting up to 25 people on-site during the second round. The winner of the on-site round will be awarded a special prize.

If you are interested in job opportunities/intern positions in MemSQL (San Francisco and Seattle) please fill in the form http://codeforces.me/memsql2017/apply or you can do it during the registration on the round.

Round 1 has started!

There are 7 problems scored as 500-750-1000-1500-2000-2750-3000. The problems were prepared by pieguy with help from cerealguy and nika. Big thanks to KAN for helping with the contest and cyand1317, vintage_Vlad_Makeev, Arpa for testing.

Hi, everyone!

On September 10, 2017 at 13:00 Moscow time the final round of Russian Code Cup 2017 will take place! The round will be 3 hours long. 55 participants of the final round will compete for prizes and glory, and we are eager to watch their competition at http://russiancodecup.ru.

And we have a nice surprise for the others: if you would like to apply your skills at our finals problems, come to codeforces.com after the Finals is over, at 16:35 Moscow time, the round featuring RCC Finals 2017 problems will take place, open for everybody.

Some notes:

• Round will use ACM rules;
• It will be unrated;
• Problem difficulty will be close to Div 1 round;
• We ask RCC finalists not to publish or discuss problems after the end of the Finals before the CF round ends, of course you shouldn't participate in CF round;
• Judging machines at RCC and CF are different, "my solution passed/failed at CF, and it was different at RCC" is not a valid appeal.

UPD The official contest is over, congratulations to the winners! And good luck to CF Round participants.

UPD2 Editorial

Hi everybody!

These days Moscow is conducting the 2nd International Olympiad of Metropolises that is an international competition for high school students from biggest cities and capitals all around the world. One of the disciplines of the competition is informatics. Rounds of the competition were prepared by the jury members invited from St. Petersburg, Minsk, Almaty and Moscow olympiad scientific committee which you may know by Moscow team Olympiad, Open Olympiad in Informatics and Moscow Olympiad for young students (rounds 327, 342, 345, 376, 401).

We are very grateful to MikeMirzayanov for Polygon system that made it possible to conveniently hold a simultaneous statement translation process into lots of languages. As a good friends of Codeforces platform, we conduct a parallel rated Div. 1 + Div. 2 round on the competition problemset.

Round will happen on September 6th at 12:55 UTC and it will last for two hours. There will be 5 problems for each division, scoring will be announced later.

Scientific Committee of the olympiad consists of: andrewzta, GlebsHP, Endagorion, meshanya, Chmel_Tolstiy, Zlobober, Helen Andreeva and Bakhyt Matkarymov. Problems were prepared by timgaripov, mingaleg, halin.george, vintage_Vlad_Makeev, malcolm, LHiC coordinated by your humble servant.

Codeforces coordinator KAN helped us to choose problems for a round.

Good luck and high ratings for everybody!

PS We kindly ask everybody who knows problems of an on-site event not to participate in a round and not to discuss them in public, as this may be a subject for disqualification.

Congratulations to the winners!

In div. 1 they are:

1. Um_nik
2. fateice
3. KADR
4. dotorya
5. FallDream

In div. 2 they are:

1. jiangIy
2. xolm
3. yxqk
4. lixolas
5. Rawnd

The analysis is published. Thanks to all for participating!

Hello Codeforces!

On September 05, 18:05 MSK Educational Codeforces Round 28 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.

The round will be unrated for all users and 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 6 problems and 2 hours to solve them.

The problems were prepared by Mikhail awoo Piklyaev, Vladimir vovuh Petrov and me.

Good luck to all participants!

UPD. Editorial can be found here.

Congratulations to the winners:

Congratulations to the best hackers:

169 successful hacks and 113 unsuccessful hacks were made in total!

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

Hi!

I'm honored to invite you to Codeforces Round #432, it will be held on 4th September 14:35 UTC. There will be 5 problems for each division, as usual, you have 2:30 to solve the problems. The contest was prepared by Lewin Lewin Gan, Artsem Arterm Zhuk and me.

The IndiaHacks Final Round will be held on 3rd September 12:30. Finalist must not discuss the problems after their contest.

The stories of my problems will be about Arpa, although in one problem you'll see Mojtaba moji FayazBakhsh, my great teacher.

I'd like to thank Lewin, Artsem and myself (:P) at first, then Konstantin zemen Semenov and WHITE2302 for testing the problems, Nikolay KAN Kalinin for helping us in moving the contest to codeforces and Mike MikeMirzayanov Mirzayanov for the great Codeforces and Polygon platforms.

The scoring distribution will be announced later.

Obviously, if you are interested in if the round is rated or not, ask in comments and get a lot of down votes.

UPD. There will be 5 problems for div.2 and 6 problems for div.1.

UPD2. Scoring Distribution: div.1: 500-1000-1250-1750-2000-2500, div.2: 500-1000-1500-2000-2500.

UPD3. Editorial is partially ready. I'll complete it soon.

Congratulations to winners:

Div.1:

1 . BaconLi

2 . dreamoon_love_AA

3 . sd0061

4 . W4yneb0t

5 . Um_nik

Div.2:

1 . miaom

2 . fzzzq2002

3 . lzy960601

4 . Lucas97 and Szymanski_w (WoW !!)

Official results

Hi Codeforces!

It's our pleasure to announce the 10th edition of Bubble Cup. Bubble Cup is a programing competition organized by Microsoft Development Center Serbia (MDCS), and will be held this weekend. Contest will take place on Saturday, 2nd of September at 09:30 UTC, in Belgrade, Serbia. Live results will be available on the official Bubble Cup website (results will be frozen during the last hour of the competition). Winners will be announced at the closing ceremony.

Just like the two previous editions, this final will be followed by an online mirror competition on Codeforces. Mirror will take place on Sunday, 3rd of September at 10:00 UTC. Contest will last for 5 hours and ACM ICPC rules will be applied. It will be a competition for teams of 1-3 members. There will be at least eight problems.

We kindly ask participants of the onsite final to hold off discussing problems publicly until the mirror is over.

Contest was mainly prepared by employees of MDCS. We give our thanks to Nikolay Kalinin (KAN) for the round coordination, Mike Mirzayanov (MikeMirzayanov) and the team behind Codeforces and Polygon platforms. Special thanks goes to knightL for helping out with problem testing.

The contest will be unrated. The reason for this is because rules of this contest are not common for Codeforces. Also, it is only a mirror of an onsite competition.

Editorial will be available in the booklets section on the Bubble Cup website a few hours after the online mirror ends.

EDIT:
Here you can find mirror contests from the previous two finals:
Bubble Cup 8 — Finals [Online Mirror]
Bubble Cup 9 — Finals [Online Mirror]

EDIT #2:
The contest has started. You can see the live results on the Bubble Cup website.

EDIT #3:
Here are the results of the onsite finals.

The top three winning teams of the online mirror contest:
1. tourist, VArtem
2. zigui, molamola., dotorya
3. Um_nik, Kronecker
Complete rankings are listed on this link.

Congrats to all winners!

You can find contest editorial here.

EDIT #4:
Thank you for your comments. While our official and ainta's solution matched on the test cases provided we found out from the comments here that there are some edge cases we didn't handle correctly and don't know how to handle properly given the constraints. Because of that we decided to remove the problem from the set and reset all penalties people received from the incorrect submissions. Sincere apologies to everyone affected by this.

Hi!

I’d like to invite you to Codeforces Round #431 which takes place at 16:35 MSK on 1 September. Please note that the timing is again unusual.

One of the problems is created by adedalic and KAN, while the others are authored by me. This is my second round here, and it couldn’t have been realized without efforts of: AlexFetisov, ifsmirnov, Tommyr7, winger and wu_qing who tested the problems; KAN who appears to be a meticulous guide throughout the preparation process; and MikeMirzayanov with the supercalifragilisticexpialidocious Codeforces and Polygon platforms — my deep gratitude to you!

Both divisions are welcomed as rated contestants and will have five problems to solve in two hours. The scoring will be announced later.

Once upon a time, in a virtual galaxy far, far away, there was a lovely young singer by the name of Hatsune Miku. One lovely day, Miku got a job as a vocalist in Vocaloid, and that was very exciting. People said, “Oh, Miku, you sing so accurately! And so emotive, too!” Soon everyone was talking about Miku, and there were songs and paintings and even live concerts for, and with, Miku. Miku liked that.

And you, are to start a journey following the emotions in Miku’s voice. Oh, by the way, a late Happy Birthday to her — August 31 is (was) her tenth anniversary.

For the world you live in, thank you.

See you then, and wish everyone few bugs and fair ratings.

UPD 1 Scoring will be:

• 500-1000-1500-2000-2500 for Division 2;
• 500-1000-1750-1750-2500 for Division 1.

UPD 2 System test is done. Congratulations to the winners!

Division 1

1. dotorya
2. Reyna
3. SkyDec
4. V--o_o--V
5. ko_osaga

Division 2

1. lmmortalCO (solved all problems!)
2. ltg2030
3. FoolMike
4. HatsuneMiku
5. MisakaKuma

Also, thanks to all who participated! Nicely done!

Check out the editorial with hints!

UPD 3 Complete tutorials and behind-the-scene fragments are out. Problem packages may be published soon, stay tuned!

Hi everybody!

On August 29, в 18:05 MSK Codeforces Round #430 (Div. 2) will be held. As usual, Div.1 participants can join out of competition.

The problems are prepared by me Glebodin and Ilya Ilua Maximov. Many thanks to Alexey Perforator Ripinen for help in preparations of the round. Great thanks to Alexey Livace Ilyukhov, Ildar 300iq Gainullin, Daniil qoo2p5 Nikolenko for testing the round, Nikolay KAN Kalinin for helping us preparing the round, Maxim HellKitsune Finutin and Ivan BledDest Androsov for testing this round and Mike MikeMirzayanov Mirzayanov for the Codeforces and Polygon systems.

The scoring is : 500 — 1000 — 1500 — 2000 — 2500

Congratulations to the winners:

Div. 1:

uwi

vintage_Vlad_Makeev

natsugiri

kmjp

victoragnez

Div. 2:

fatego

sufficiently_large_boss

qscqesze6

white_flag

Panole2333330

Editorial : http://codeforces.me/blog/entry/54179