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