Problem:
Greatest Common Divisor

Write a program which finds the greatest common divisor of two natural numbers a and b

Input

a and b are given in a line sparated by a single space.

Output

Output the greatest common divisor of a and b.

Constrants

1 ≤ a, b ≤ 109

Hint

You can use the following observation:

For integers x and y, if x ≥ y, then gcd(x, y) = gcd(y, x%y)

Sample Input 1

54 20

Sample Output 1

2

Sample Input 2

147 105

Sample Output 2

21

Solution in Python3 (judge verdict: Accepted)

# coding: utf-8

def getGCM(a, b):
    if b > a:
        a, b = b, a
    while True:
        r = a % b
        if r == 0:
            return b
        else:
            a = b
            b = r

x, y = map(int,input().rstrip().split())
print(getGCM(x, y))