input: Write a function to find the greatest common divisor (GCD) of two numbers using the recursive Euclidean algorithm. If the second number is zero, then return the first number as the GCD. Otherwise, recursively call the function with the second number and the remainder of the division of the first number by the second.
  def findGCD(a, b): 
     if (b == 0): 
         return a
     return findGCD(b, a % b)
  
  assert findGCD(1000, 500) == 500
  assert findGCD(8, 36) == 4
  assert findGCD(7, 13) == 1
  assert findGCD(20, 0) == 20
  assert findGCD(0, 15) == 15
output: def findGCD(a, b): 
     if (b == 0): 
         return a
     return findGCD(b, a % b)