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)

def greatest_common_devisor(x, y):
    if y == 0:
        return x
    x, y = y, x % y
    return greatest_common_devisor(x, y)
x, y = map(int, input().split(' '))
if x < y:
    tmp = x
    x = y
    y = tmp
print(greatest_common_devisor(x, y))