'''gcd iterative and recursive variations'''
# Here is an iterative solution

def gcd(a,b):
  """Returns the gcd of its inputs times the sign of b if b is nonzero,
  and times the sign of a if b is 0.
  """
  while b != 0:
      a,b = b, a % b
  return a


# Here is a recursive solution

def gcdr(a,b):
  """Returns the gcd of its inputs times the sign of b if b is nonzero,
  and times the sign of a if b is 0.
  """
  if b == 0:
    return a
  else:
    return gcdr(b, a % b)