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 = map(int, input().split())
slist = []
if (a > b):
    c = a%b
    d = b
    while (c != 0 and d != 0):
        if (c < d):
            d = d%c
        elif (c > d):
            c = c%d
    if(c == 0):
        print(d)
    elif(d == 0):
        print(c)
        
    
elif(a < b):
    c = a
    d = b%a
    while (c != 0 and d != 0):
        if (c < d):
             d = d%c
        elif (c > d):
            c = c%d
    if(c == 0):
        print(d)
    elif(d == 0):
        print(c)
        
else:
    print(a)