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 Python (judge verdict: Accepted)

def gcd(a,b):
    c = a % b
    if c == 0:
        return b
    else:
        return gcd(b, c)
    
if __name__ == "__main__":
    import sys
    a, b = [ int(e) for e in sys.stdin.readline().strip().split() ]
    print gcd(max(a,b), min(a,b))