#include<bits/stdc++.h>
using namespace std;
int main()
{
int n,i=1,s=0,d,f;
cin>>n;
while(i<=n){
		f=2;
		d=1;
	while(f<=i){
		d*=f;
		f++;
	}
	s+=d;
	i++;
}
cout<<s;

return 0;
}
/**************************************************************
	Problem: 1019
	User: zzz1
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/