今天让 o1 做一道新出来的 cf 题，很简单 given a, construct an array b such that for every index i, the element a[i] is one of the modes of the subarray [b[1], b[2], ..., b[i]]. 但是 it fails to find a neet way to solve 就是让every 1 to n都出现一遍就行