BZOJ 3817 - Sum
2017-03-31
题目地址
描述 给定正整数 n , r ( n ≤ 1 0 9 , r ≤ 1 0 4 ) n, r(n\le {10}^9, r \le {10}^4) n , r ( n ≤ 1 0 9 , r ≤ 1 0 ......
