Codeforces Round #503 (based on SIS olympiad)

Revision en8, by cdkrot, 2018-08-12 15:10:09


Summer Informatics School (SIS / LKSH) is a summer school for students in grades 6-10. SIS is focused mainly (but not only) on students participating in the Olympiads in Informatics — from beginners to participants of international competitions. SIS is held in July and August, each of them is visited by about 200 students from all over Russia and abroad. The language of the camp is Russian. Additional information about SIS is posted at

Right now, the August branch of the Summer Computer School is running, and on August 11 the traditional team Olympiad is going to place. I am happy to present a rated round based on it!

The round will be rated for both divisions, will be held in Aug/11/2018 16:35 (Moscow time), in each division there will be 5 tasks and 2 hours to solve them.

The problems of this round and the SIS olympiad were authored and prepared by SIS's teachers: izban, achulkov2, Schemtschik, peltorator, craborac, asokol, Morokei, Burunduk2. Also, I would like to thank Kurpilyansky for his help with olympiad's organization.

Thanks to our problems testers: meshanya, Burunduk2, vintage_Vlad_Makeev, niyaznigmatul, manoprenko!

Thank you, MikeMirzayanov, for the codeforces and polygon systems!

Yes, we are aware, that this contest clashes with ProCon Junior on codechef. However, given the schedule of the SIS and the approaching VK cup finals we can't do anything with it, sorry for that =/

Good luck!

UPD: The round will have one interactive problem for both divisions. Please, read the post about interactive problems here: Interactive Problems: Guide for Participants.

Congratulations to winners!


  1. Marcin_smu
  2. Radewoosh
  3. Swistakk
  4. Panole233
  5. ko_osaga


  1. wnsh
  2. aurelio
  3. usachevd0
  4. jebouin
  5. etiennerossignol

Upd Thank you for participation! Due to vk-cup conduction rating recalculation will happen slightly later, than usually.

Upd The editorial is published!

You may also check the unofficial editorial, written by neal.


  Rev. Lang. By When Δ Comment
en8 English cdkrot 2018-08-12 15:10:09 211
ru12 Russian cdkrot 2018-08-12 15:09:08 217
ru11 Russian cdkrot 2018-08-11 22:23:46 2 Мелкая правка: 'нг состоит немного п' -> 'нг состоится немного п'
en7 English cdkrot 2018-08-11 19:48:31 127
ru10 Russian cdkrot 2018-08-11 19:47:34 111
en6 English cdkrot 2018-08-11 19:28:15 374
ru9 Russian cdkrot 2018-08-11 19:27:18 371
ru8 Russian cdkrot 2018-08-11 03:05:01 25 Мелкая правка: '018-08-11], [user:_kun_,2018-08-11]' -> '018-08-11]'
en5 English cdkrot 2018-08-11 03:04:44 25 Tiny change: '018-08-11], [user:_kun_,2018-08-11]' -> '018-08-11]'
en4 English cdkrot 2018-08-11 01:07:48 54 Tiny change: '018-08-09]. Also, I' -> '018-08-09], [user:burunduk2], [user:_kun_]. Also, I'
ru7 Russian cdkrot 2018-08-11 01:07:11 54 Мелкая правка: '018-08-09]. Также с' -> '018-08-09], [user:burunduk2], [user:_kun_]. Также с'
en3 English cdkrot 2018-08-10 02:10:56 411
ru6 Russian cdkrot 2018-08-10 02:07:23 224
ru5 Russian cdkrot 2018-08-10 02:04:24 190
en2 English cdkrot 2018-08-09 10:56:40 17 Tiny change: '9], [user:Peltorator,2018-08-0' -> '9], [user:i_love_isaf27,2018-08-0'
ru4 Russian cdkrot 2018-08-09 10:56:16 17 Мелкая правка: '9], [user:Peltorator,2018-08-0' -> '9], [user:i_love_isaf27,2018-08-0'
ru3 Russian cdkrot 2018-08-09 02:22:35 1 Мелкая правка: 'Школы и 11го августа' -> 'Школы и 11-го августа'
ru2 Russian cdkrot 2018-08-09 01:40:53 32 Мелкая правка: '018-08-09]. Также с' -> '018-08-09], [user:WreckingBall]. Также с'
en1 English cdkrot 2018-08-09 01:39:58 1552 Initial revision for English translation
ru1 Russian cdkrot 2018-08-09 01:26:33 1435 Первая редакция (опубликовано)