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 sc = new Scanner(System.in);
 
        int x = sc.nextInt();
        int y = sc.nextInt();
        System.out.println(gcd(Math.max(x, y), Math.min(x, y)));
    }
 
    private static int gcd(int x, int y) {
        int r = x % y;
        if(r == 0) return y;
        return gcd(y, r);
    }
}