input: Write a function to find the GCD (Greatest Common Divisor) of two numbers using the Euclidean algorithm. If one or both of the numbers are zero, return 0 as the GCD.
  assert findGCD(1000, 500)==500
  assert findGCD(18, 22)==2
  assert findGCD(0, 20)==0
  assert findGCD(7, 0)==0
  assert findGCD(0, 0)==0
output: def findGCD(a, b):
      if a == 0 or b == 0:
          return 0
      while b != 0:
          a, b = b, a % b
      return a