1394. Find Lucky Integer in an Array

Given an array of integers arr, a lucky integer is an integer that has a frequency in the array equal to its value. Return the largest lucky integer in the array. If there is no lucky integer return -1. Example 1: Input: arr = [2,2,3,4] Output: 2 Explanation: The only lucky number in the array is 2 because frequency[2] == 2. Example 2: Input: arr = [1,2,2,3,3,3] Output: 3 Explanation: 1, 2