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 = [list(map(int, s.split())) for s in open(0)][0]
x, y = A[0], A[1]
if y > x:
    l, s = y, x
else:
    l, s = x, y
while l % s >  0:
    m = l % s 
    l = s 
    s = m
print(s)