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 main(input){
  let lines = input.split("\n");
  let x = lines[0].split(" ")[0];
  let y = lines[0].split(" ")[1];
  
  if (x < y){
        [x, y] = [y, x]
  }
  while (y > 0){
    r = x % y
    x = y
    y = r
  }
  console.log(x)
}

main(require('fs').readFileSync('/dev/stdin', 'UTF-8'));