input: Write a python function to find the greatest common divisor (GCD) of two numbers.
  assert findGCD(48, 18) == 6
  assert findGCD(101, 10) == 1
  assert findGCD(54, 24) == 6
  assert findGCD(0, 5) == 5
  assert findGCD(7, 0) == 7
output: def findGCD(a, b):
      while b:
          a, b = b, a % b
      return a