Given an array of integers citations where citations[i] is the number of citations a researcher received for their ith paper, return compute the researcher's h-index. According to the definition of h-index on Wikipedia: A scientist has an index h if h of their n papers have at least h citations each, and the other n − h papers have no more than h citations each. If there are several possible values for h, the maximum one is taken as the h-index. Example 1: Input: citations = [3,0,6,1,5] Output: 3 Explanation: [3,0,6,1,5] means the researcher has 5 papers in total and each of them had received 3, 0, 6, 1, 5 citations respectively. Since the researcher has 3 papers with at least 3 citations each and the remaining two with no more than 3 citations each, their h-index is 3. Example 2: Input: citations = [1,3,1] Output: 1 Constraints: n == citations.length 1 <= n <= 5000 0 <= citations[i] <= 1000