input: def diffHighestLowest(arr: List[int]) -> int:
      """ Calculate the difference between the highest and lowest values in a list of integers.
      >>> diffHighestLowest([12, 24, 3, 8, -1])
      25
      >>> diffHighestLowest([10, 20, 30, 40, 50])
      40
      """
output:     return max(arr) - min(arr)