Hi everyone! I was practicing with some regional contests, and today we (my team) picked the Greater New York Regional Contest 2015.

We managed to solve all but one problem. Here is the link

The statement lacks of constraints, but the offial data tests contains cases with at most 600 nodes.

We tried a brute force with no success (obviously).

Can you help me? I read the official solution but I really couldn't understand it, however it doesn't seem very complicated. Maybe I'm missing something.

Thanks!