new_contents: """Leetcode 1394. Find Lucky Integer in an Array
  Easy
  
  URL: https://leetcode.com/problems/find-lucky-integer-in-an-array/
  
  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.
  
  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 and 3 are all lucky numbers, return the largest of them.
  
  Example 3:
  Input: arr = [2,2,2,3,3]
  Output: -1
  Explanation: There are no lucky numbers in the array.
  
  Example 4:
  Input: arr = [5]
  Output: -1
  
  Example 5:
  Input: arr = [7,7,7,7,7,7,7]
  Output: 7
   
  Constraints:
  - 1 <= arr.length <= 500
  - 1 <= arr[i] <= 500
  """
  
  
  class Solution(object):
      def findLucky(self, arr):
          """
          :type arr: List[int]
          :rtype: int
          """
          pass
  
  
  def main():
      pass
  
  
  if __name__ == '__main__':
      main()
  
subject: Add lc1394_find_lucky_integer_in_an_array.py