Hello, everyone! Codeforces Round #320 will be held at Sep/16/2015 18:00 MSK. Note that round starts in the unusual time!

Bayan is an Iranian software company working on large-scale web applications. It doesn't only develop the search engine, but also it holds an annual open competition Bayan Programming Contest with an on-site round in Tehran. The on-site round of 2015 became an international event with many strong participants.

Bayan has supported Codeforces on our Codeforces 5-year crowdfunding program. Thank you Bayan! This round is in your honor!

The problems are from tmt514, Shik, drazil, and me(dreamoon_love_AA). Also we want to thank Zlobober for helping us preparing the round, anonymous(will be updated soon) testers for testing this round , Delinur for translating the statement into Russian, and MikeMirzayanov for Codeforces and Polygon.

This is my second time organizing a problemset for a Codeforces round (my previous round: #292). In the last round all problems are provided by me. But I think that if problems are provided by more people, then the contest will be more interesting! So I asked my friends to help me this time. Hope everybody can have fun during the round!

Participants in each division will be given six tasks and two and a half hours for solving them (the last four problems in Div. 2 are as same as as the first four problems in Div. 1). Scoring system will be announced later closer to the start of the round.