/*
* Run this as:
*    java Factorial
*/
public class Factorial {
    public static void main(String[] args) {
        int x = factorial(5);

        System.out.println(x);

        int y = factorial(10);

        System.out.println(y);

        System.out.println(factorial(3));
    }

    /*
    * Here is a subroutine defined. In Java, we call it a method.
    */
    public static int factorial(int x) {
        if (x == 0) {
            return 1;
        }

        return x * factorial(x - 1);
    }
}