This problem is in Contest(s) below:
Contest 2088:区一中提高组队列练习
Contest 1538:练习1
Contest 1654:clez周三下午普及练习(堆,单调队列)
Contest 1656:clez提高组练习(贪心、并查集)
Contest 1659:区一中提高组练习(单调队列)
Contest 2075:枚举算法
Contest 1757:暴力专题