C :

#include<stdio.h>
int main()
{
	double sum=0,num,i,j;
	int n;
	scanf("%d",&n);
	for (i=n;i>=1;i--)
	{
		for(j=i,num=1;j>=1;j--)
			num*=j;
		sum+=num;
	}
	printf("%.0lf\n",sum);
	return 0;
}

C++ :

#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
	int n;
	cin>>n;
	double t=1,sum=0;
	for (int i=1; i<=n; i++)
	{
		t*=i;
		sum+=t;
	}
	printf("%.0lf\n",sum);
	return 0;
}