#include <bits/stdc++.h>
using namespace std;
int main()
{
	int n,x,x1,s=1,ss=0;
	cin>>n;
	for(int i=1;i<=n;i++){
		s=1;
		for(int j=1;j<=i;j++){
			s*=j;
		}
		ss+=s;
	}
		
	cout<<ss;
	return 0;
}
/**************************************************************
	Problem: 1019
	User: lcy
	Language: C++
	Result: Accepted
	Time:18 ms
	Memory:2072 kb
****************************************************************/