input: Write a function to recursively find the greatest common divisor (GCD) of two given numbers. The function should take two integer inputs and return the GCD. If either of the numbers is 0, the function should return the other number as the GCD.
  
  def findGCD(a, b):
      if b == 0:
          return a
      return findGCD(b, a % b)
  
  assert findGCD(1000, 500) == 500
  assert findGCD(20, 15) == 5
  assert findGCD(0, 10) == 10
  assert findGCD(29, 0) == 29
  assert findGCD(9, 27) == 9
output: def findGCD(a, b):
      if b == 0:
          return a
      return findGCD(b, a % b)