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 scanner = new Scanner(System.in);
        int x = Integer.parseInt(scanner.next());
        int y = Integer.parseInt(scanner.next());

        if (x == y) {
            System.out.println(x);
            return;
        }

        if (x < y) {
            int tmp = x;
            x = y;
            y = tmp;
        }

        while (true) {
            int z = x % y;
            if (x % z == 0 && y % z == 0) {
                System.out.println(z);
                break;
            }
            x = y;
            y = z;
        }
    }
}