Good morning (day, evening, night)!

Today's round problems authors are we — Rei and yaro. We've been thoroughly selecting the problemset, so hope you'll enjoy the final edition.

Thanks to problem coordinator Artem Rakhov for invaluable help in round preparation, and to those, who makes codeforces more comfortable, functional and stable.

Wish you good luck!

Today's round problems authors are we — Rei and yaro. We've been thoroughly selecting the problemset, so hope you'll enjoy the final edition.

Thanks to problem coordinator Artem Rakhov for invaluable help in round preparation, and to those, who makes codeforces more comfortable, functional and stable.

Wish you good luck!

**UPD.**Analysis: A B C D E
coord <= 4instead ofcoord <= 5, then got challenged =)In problem C , almost everyone wrote same 2 line solution.

Alas, I did not give it a try.(the idea could have struck me too :( )

By the way, excelent contest, nice problems.

http://ace.delos.com/TESTDATA/OPEN10.tricount.htm

http://www.topcoder.com/wiki/display/tc/TCO'10+Online+Round+4

UPD:I see.may I know if there is a proof for problem C? I am not sure how you can derive the answer.

Thanks!