input: Write a function to find the GCD (Greatest Common Divisor) of two numbers using the Euclidean algorithm. The function should take two integers as arguments and return the GCD.
  
  def findGCD(a, b): 
     if (b == 0): 
         return a
     return findGCD(b, a % b)
  
  assert findGCD(1000, 500)==500
  assert findGCD(20, 8)==4
  assert findGCD(24, 36)==12
  assert findGCD(17, 13)==1
  assert findGCD(10, 0)==10
output: def findGCD(a, b): 
     if (b == 0): 
         return a
     return findGCD(b, a % b)