摘要：
Polycarp wrote on the board a string ss containing only lowercase Latin letters ('a'-'z'). This string is known for you and given in the input. After 阅读全文
摘要：
Problem Statement Let NN be a positive odd number. There are NN coins, numbered 1,2,…,N1,2,…,N. For each ii (1≤i≤N1≤i≤N), when Coin ii is tossed, it c 阅读全文
摘要：
Description YYF is a couragous scout. Now he is on a dangerous mission which is to penetrate into the enemy's base. After overcoming a series difficul 阅读全文