input: def diffHighestLowest(arr: List[int]) -> int:
      """ Calculate the difference between the highest and lowest values in a given array of integers.
      >>> diffHighestLowest([12, 24, 3, 8, -1])
      25
      >>> diffHighestLowest([1, 2, 3, 4, 5])
      4
      >>> diffHighestLowest([-5, -3, -1, -10])
      7
      """
output:     return max(arr) - min(arr)