input: 
  def findGCD(a, b):
      """Find the Greatest Common Divisor (GCD) of two numbers using the Euclidean algorithm.
      >>> findGCD(1000, 500)
      500
      >>> findGCD(252, 105)
      21
      >>> findGCD(9, 12)
      3
      """
      if b == 0:
          return a
      return findGCD(b, a % b)
  
output:     if b == 0:
          return a
      return findGCD(b, a % b)