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 input = new Scanner(System.in);
        int a = input.nextInt();
        int b = input.nextInt();
       System.out.println(gcd(a,b));
    
       
    
       
    }//main
    
     public static int gcd(int a,int b){
            if(b == 0){
                return a;
            }//if
            return gcd(b, a % b);
        }//gcd
    
}//main