class Solution:
    def hIndex(self, citations):
        if len(citations)==1:
            if citations[0]==1:
                return 1
            if citations[0]==0:
                return 0
        citations.sort(reverse=-1)
        h=0
        for i in range(len(citations)):
            if citations[i]<i+1:
                h=i
                break
        if citations[-1]>=len(citations):
            return len(citations)
        return h