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)

from collections import defaultdict

def gcd(x,y):
    if max(x,y) % min(x,y) == 0 : return min(x,y)
    else : return gcd(min(x,y) ,max(x,y)%min(x,y))

if __name__ == '__main__' :
        a,b = [int(i) for i in input().split(" ")]
        print(gcd(a,b))