input: 
  def diffHighestLowest(arr: List[int]) -> int:
      """ Calculate the difference between the highest and lowest values in the given list of integers.
      >>> diffHighestLowest([12, 24, 3, 8, -1])
      25
      >>> diffHighestLowest([0, 0, 0, 0])
      0
      """
      lowest = min(arr)
      highest = max(arr)
      return highest - lowest
  
output:     lowest = min(arr)
      highest = max(arr)
      return highest - lowest