Educational Codeforces Round 8 will take place on 19 February 2016 at 18:00 MSK for the first and the second divisions. You can read about educational rounds here and here. I hope that the high density of contests on Codeforces will not startle you and you will participate in ER8.
<The phrase about simple problems is added in the end>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to me.
It seems that it is harder to invent interesting simple problems (like A and B) than difficult ones. So don't be afraid to suggest interesting simple or very simple tasks.
</The phrase about simple problems is added in the end>
This time (for the first time) the problemset was totally suggested by Codeforces users. The problem А suggested by user unprost. The problem B was taken form the problems sent by Bayram Berdiyev Bayram, Allanur Shiriyev Allanur-98, Bekmyrat Atayev Bekmyrat-Atayev. The problem D suggested by Kareem Mohamed Kareem_Mohamed95 (but I made it more difficult to make it more interesting for you :-)). The problem E sent Ali Ahmadi Kuzey. The problems C and F are suggested by Kamil Debowski Errichto.
Thanks a lot to them and all others who are sending the problems or just ideas of the problems!
This time the problems wasn't prepared only by me (Edvard Davtyan). Thanks a lot to Kamil Debowski Errichto who not only suggested the problems C and F, but also prepared them. Thanks to Maria Belova Delinur for checking the English statements. Also thanks a lot to Ali Ahmadi Kuzey who helped me with testing of some problems.
A few words about the problems: A) Easy problem with the long statement; B) I hope you will not write hard solution; C) It's interesting; D) It's a little technical, but contains very useful technique; E) I like this problem; F) Very cool problem if you will not solve during the contest I recommend to solve it in practice.
Good luck and have fun!
UPD1: The first phase of the contest finished. Hacks started. The editorial is ready.
By the reason that all the problems of Errichto are about a bears, below you can see the illustration for the problem C (it seems Limak is the leftmost):