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)

//config = {input: 'tmp', newline: '\r\n'}; // win
config = {input: '/dev/stdin', newline: '\n'}; //linux

line = require('fs').readFileSync(config.input, 'ascii')
  .split(' ')
  .map(Number);

function gcd(x, y) {
  if (y > x) gcd(y, x);
  if (y % x === 0) return x;
  return gcd(y, x % y);
}

console.log(gcd(line[0], line[1]));