input: Write a function to calculate the GCD of two numbers using the Euclidean algorithm. The function should take two integers as input and return their GCD. If the second number is 0, the function should return the first number.
  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(9, 28) == 1
  assert findGCD(12, 0) == 12
  assert findGCD(0, 0) == 0
output: def findGCD(a, b): 
     if (b == 0): 
         return a
     return findGCD(b, a % b)