#import "bits/stdc++.h"
#define ll long long
using namespace std;
ll sum = 1;
ll jc(ll n){
	ll sum=1;
	for(int i=2;i<=n;i++)sum*=i;
	return sum;
}
signed main(){
	ll n,cos=3;
	cin >> n;
	for(int i=3;i<=n;i++)cos+=jc(i);
	cout << cos;
	return 0;
}