摘要：
[Codeforces Round 620 (Div. 2)] E. 1 Trees and Queries time limit per test 4 seconds memory limit per test 512 megabytes input standard input output s 阅读全文
摘要：
AtCoder Beginner Contest 155 D Pairs ， E Payment 题解 D Pairs We have NN integers A1,A2,...,ANA1,A2,...,AN. There are N(N−1)2N(N−1)2 ways to choose two 阅读全文