input: Write a function to find the GCD (Greatest Common Divisor) of two numbers using the Euclidean algorithm.
  
  def findGCD(a, b): 
     if (b == 0): 
         return a
     return findGCD(b, a % b)
    
  assert findGCD(1000, 500) == 500
  assert findGCD(14, 28) == 14
  assert findGCD(48, 18) == 6
  assert findGCD(7, 5) == 1
  assert findGCD(0, 0) == 0
output: def findGCD(a, b): 
     if (b == 0): 
         return a
     return findGCD(b, a % b)