#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<windows.h>

int Add_Factorial(int n)
{
    int sum = 1;
    int i =1;
    int ret = 1;
    for (i = 2; i <= n; i++)//加至n
    {
        ret *= i;//每次在前一個數階乘的基礎上再乘以i
        sum += ret;//前i個數的和
 

    }
    return sum;

}

int main()
{
    int num = 0;
    printf("Please Enter a Number:>");
    scanf("%d",&num);
    printf("result = %d\n",Add_Factorial(num));
    system("pause");
    return 0;
}