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.*;
import java.util.Scanner;

public class Main {
    public static void main (String args[]) {
        // input

        int a;
        int b;

        Scanner inp = new Scanner(System.in);

        a = inp.nextInt();

        b = inp.nextInt();

       while (b != 0) {
           int temp = a;
           a = b;
           b = temp%b;
       }

       System.out.println(a);
    }
}