Leetcode 1394. Find Lucky Integer in an Array

class Solution:
    def findLucky(self, arr: List[int]) -> int:
        counts = Counter(arr)
        res = -1
        for k, v in counts.items():
            if k == v:
                res = max(res, k)
                
        return res

https://leetcode.com/problems/find-lucky-integer-in-an-array/