Java 代码

import java.util.Scanner;

public class Main
{   
    public static int fact(int n)
    {
        if (n == 1)
            return 1;
        else
            return n * fact (n -1 );
    }

    public static void main(String[] args)
    {
        Scanner cin = new Scanner(System.in);

        int n = cin.nextInt();

        System.out.println (fact (n));
    }
}