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)

Z= input().split()
X=int(Z[0])
Y=int(Z[1])
while(X!=Y):
    if(X>Y):
        R=X-Y
        X=Y
        Y=R
    elif(X<Y):
        R=Y-X
        Y=R
print(Y)