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)

a, b = [int(i) for i in input().split()]

z = 0

def gcd(x,y):
    if x<y:
        z=x
        x=y
        y=z

    while x%y !=0:
        z=x%y
        x=y
        y=z
        gcd(x,y)
    return y

print(gcd(a,b))