求阶乘和

import java.util.Scanner;public class Pat_Test {    public static void main(String[] args) {        Scanner in = new Scanner(System.in);        int N = in.nextInt();        int sum = 0;        int mul = 1;        int j = 1;        for(int i = 1;i <= N ;i++){            while(j<=i)              {               mul=mul*j;               j++;              }            sum = sum + mul;        }        System.out.println(sum);    }}