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.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int[] num = new int[2];

        for(int i = 0; i < num.length; i++){
            num[i] = sc.nextInt();
        }

        System.out.println(gcd(num[0],num[1]));
    }
    
    public static int gcd(int x, int y){
        int r;
        if(x < y){
            int tmp = x;
            x = y;
            y = tmp;
        }
        while(y > 0){
            r = x % y;
            x = y;
            y = r;
        }
        return x;
    }
}