Hello, everyone! Codeforces Round #320 will be held at [Sep/16/2015 18:00 MSK](http://timeanddate.com/worldclock/fixedtime.html?day=16&month=9&year=2015&hour=18&min=0&sec=0&p1=166). Note that round **starts in the unusual time**!↵
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The problems are from [user:tmt514,2015-09-15], [user:shik,2015-09-15], [user:drazil,2015-09-15], and me([user:dreamoon,2015-09-15]). Also we want to thank [user:Zlobober,2015-09-15] for helping us preparing the round, [user:AlexFetisov,2015-09-15] and [user:winger,2015-09-15] for testing this round , [user:delinur,2015-09-15] for translating the statement into Russian, and [user:MikeMirzayanov,2015-09-15] for Codeforces and Polygon.↵
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This is my second time organizing a problemset for a Codeforces round (my previous round: [#292](http://mirror.codeforces.com/blog/entry/16446)). Inthe lastmy previous round all problems awere 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!↵
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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.↵
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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 <a href="http://contest.bayan.ir/en/">Bayan Programming Contest</a>↵
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!↵
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The problems are from [user:tmt514,2015-09-15], [user:shik,2015-09-15], [user:drazil,2015-09-15], and me([user:dreamoon,2015-09-15]). Also we want to thank [user:Zlobober,2015-09-15] for helping us preparing the round, [user:AlexFetisov,2015-09-15] and [user:winger,2015-09-15] for testing this round , [user:delinur,2015-09-15] for translating the statement into Russian, and [user:MikeMirzayanov,2015-09-15] for Codeforces and Polygon.↵
↵
This is my second time organizing a problemset for a Codeforces round (my previous round: [#292](http://mirror.codeforces.com/blog/entry/16446)). In
↵
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.↵
↵
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 <a href="http://contest.bayan.ir/en/">Bayan Programming Contest</a>↵
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!↵
