input: def findGCD(a: int, b: int) -> int:
      """ Compute the greatest common divisor (GCD) of two numbers.
      >>> findGCD(1000, 500)
      500
      >>> findGCD(20, 8)
      4
      """
      if (b == 0): 
          return a
      return findGCD(b, a % b)
output:     if (b == 0): 
          return a
      return findGCD(b, a % b)