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: Runtime Error)

z=list(map(int,input().split()))
z.sort()
a=0

while True:
    a=z[1]-z[0]
    if z[0]%a==0:
        z[1] = z[0]
        z[0] = a
        z.sort()
        break
    z[1]=z[0]
    z[0]=a
    z.sort()

print(z[0])