#include <bits/stdc++.h>
using namespace std;
int main()
{
int n,sum=0;
cin>>n;
for(int i=1;i<=n;i++){
	int k=1;
	for(int j=1;j<=i;j++){
		k*=j;
		
	}sum+=k;
}
cout<<sum<<endl;
return 0;
}

/**************************************************************
	Problem: 1019
	User: mc002
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/