input: from typing import Tuple
  
  def findGCD(a, b): 
     """
     Find the greatest common divisor (GCD) of two numbers using the Euclidean algorithm.
     >>> findGCD(1000, 500)
     500
     """
     if (b == 0): 
         return a
     return findGCD(b, a % b)
  
  # Example usage
  a = 1000
  b = 500
  print("GCD of number is: ", findGCD(a, b))
output:     while b != 0:
          a, b = b, a % b
      return a