Problem 189A — Cut Ribbon

The problem is to maximize x+y+z subject to ax+by+cz=n. Constraints are low, so simply iterate over two variables (say x and y) and find the third variable (if any) from the second equation. Find the maximum over all feasible solutions.

Other approaches: Use dynamic programming with each state being the remainder of ribbon. Select the next piece to be a, b or c.

Problem 189B — Counting Rhombi

Observe that lots of rhombi have the same shape, but are in different locations.

What uniquely determines the shape of a rhombus? Its width and its height.

Is it possible to build a rhombus with every width and every height such that the vertices of the rhombus are in integer points?

Hello everyone,

We are glad to invite you to participate in today’s round.

Problems have been prepared by poopi, Mohammad_JRS, Gerald and me. The hero of our contest is called “PMP”. It is actually the base of our team name through the last five years. The stories are metaphoric, but they have some traces in truth.

This Codeforces round, is the last round before the incoming ICPC world final. Our best wishes for all participants of that contest, too.

I want to specially thank Gerald for his helps and advices in problem preparation, Delinur for translation of statements into Russian and MikeMirzayanov for this great system.

And we have a modified version of Burunduk1 ’s advice: “to make the round even more interesting for us, read the statements of ALL problems.” :)

We hope you enjoy the problems and have high ratings.

Update: Contest is over. Thanks to everyone for taking part and congratulations to the winners of both divisions, specially peter50216 for being the only who solved all the problems of division 1! :)

Update: Editorial