input: Write a function to find the GCD of two numbers. Use recursion and the Euclidean algorithm to determine the GCD.
  
  assert findGCD(1000, 500) == 500
  assert findGCD(12, 15) == 3
  assert findGCD(24, 36) == 12
  assert findGCD(81, 27) == 27
  assert findGCD(0, 7) == 7
output: def findGCD(a, b):
      if b == 0:
          return a
      else:
          return findGCD(b, a % b)