摘要：
Vus the Cossack has two binary strings, that is, strings that consist only of "0" and "1". We call these strings aa and bb. It is known that |b|≤|a||b 阅读全文
摘要：
You are given a tree (an undirected connected acyclic graph) consisting of nn vertices. You are playing a game on this tree. Initially all vertices ar 阅读全文