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(x,y));
        sc.close();
    }   
    public static void swap(int x,int y){
    int tmp=x;
        x=y;
        y=tmp;
    }
    public static int gcd(int x,int y){
        if(x<y){
        swap(x,y);
    }
        while(y>0){
        int r=x%y;
            x=y;
            y=r;
        }  
        return x;
        }
    }