1856D

[洛谷传送门](https://www.luogu.com.cn/problem/CF1856D "洛谷传送门") [CF 传送门](https://codeforces.com/problemset/problem/1856/D "CF 传送门") 直接求最大值不好求。我们可以采用一个交互常见的套 ......