input: Write a function to find the GCD (Greatest Common Divisor) of two numbers using the Euclidean algorithm. Implement the function recursively. If the second number is 0, the first number is the GCD. Otherwise, recursively call the function with the second number and the remainder of the first number divided by the second number.
  
  def findGCD(a, b): 
     if (b == 0): 
         return a
     return findGCD(b, a % b)
  
  assert findGCD(1000, 500) == 500
  assert findGCD(14, 21) == 7
  assert findGCD(81, 153) == 9
  assert findGCD(99, 0) == 99
  assert findGCD(0, 56) == 56
output: def findGCD(a, b): 
     if (b == 0): 
         return a
     return findGCD(b, a % b)