#!/usr/bin/env python
# -*- coding: UTF-8 -*-
def gcd(a, b):
"""Calculate the Greatest Common Divisor of a and b.
Unless b==0, the result will have the same sign as b (so that when
b is divided by it, the result comes out positive).
"""
while b:
a, b = b, a%b
return a
n1=210
n2=126
print(gcd(n1, n2))