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 JavaScript (judge verdict: Accepted)

(function(input) {
    var p = input.split(' ').map(Number);
    var x = p.shift();
    var y = p.shift();
    console.log(greatestCommonDevisor(x, y));
})(require('fs').readFileSync('/dev/stdin', 'utf8'));

function greatestCommonDevisor(x, y) {
    return Math.max.apply(null, commonDevisor(x, y));
}

function commonDevisor(x, y) {
    if (x > y) {
        x = x % y;
    } else if (x < y) {
        var tmp = y;
        y = x;
        x = tmp % x;
    }
    var a = [];
    for (var i = 1; i <= x; i++) {
        if (x % i === 0 && y % i === 0) {
            a.push(i);
        }
    }
    return a;
}