https://atcoder.jp/contests/abc280/tasks/abc280_d https://atcoder.jp/contests/abc280/tasks/abc280_f
ACM竞赛中常见的整数公式与整数分块 算法讲解|莫比乌斯反演的前置知识——数论分块 浅谈数论分块 OI-wiki 数论分块
https://www.luogu.com.cn/training/11849#problems