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)

var input = require('fs').readFileSync('/dev/stdin', 'utf8').trim().split(' ').map(Number);

function gcd(x, y) {
  if (y === 0) {
    console.log(x);
  } else {
    gcd(y, x % y);
  }
}

gcd(input[0], input[1]);