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 a = sc.nextInt();
        int b = sc.nextInt();

        System.out.println(gcd(a, b));

    }

    public static int gcd(int x, int y){
        int r;
        if (x < y) {
            swap(x, y);
        }
        while (y > 0) {
            r = x % y;
            x = y;
            y = r;
        }
        return x;
    }
    public static void swap(int a,int b)

    {

        int temp=a;

        a=b;

        b=temp;

    }
}