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 JAVA (judge verdict: Accepted)

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        Scanner scn = new Scanner(System.in);

        int x = scn.nextInt();
        int y = scn.nextInt();
        int ans = 1;

        while(true){
            if(x == 0) {
                ans = y;
                break;
            }
            if(y == 0) {
                ans = x;
                break;
            }

            if(x > y){
                x %= y;
            }
            else{
                y %= x;
            }
        }

        System.out.println(ans);

    }
}