Given an array of integers arr, a lucky integer is an integer which has a frequency in the array equal to its value.
Return a lucky integer in the array. If there are multiple lucky integers return the largest of them. If there is no lucky integer return -1.
Input: arr = [2,2,3,4]
Output: 2
Explanation: The only lucky number in the array is 2 because frequency[2] == 2.
Input: arr = [1,2,2,3,3,3]
Output: 3
Explanation: 1, 2 and 3 are all lucky numbers, return the largest of them.
Input: arr = [2,2,2,3,3]
Output: -1
Explanation: There are no lucky numbers in the array.
Input: arr = [5]
Output: -1
Input: arr = [7,7,7,7,7,7,7]
Output: 7
1 <= arr.length <= 5001 <= arr[i] <= 500