#include <bits/stdc++.h>
using namespace std;
using ll     = long long;
using prefix = __attribute__((constructor))void;
prefix init()      {cin.tie(0),ios::sync_with_stdio(0);}

signed main(){
  ll n;
  cin>>n;
  if(n==1){
    cout<<"0\n";
    return 0;
  }
  double N=double(n-1)/2;
  cout<<ll(n*(n*n+1)/2-N*((4*N+3)*N-1)/3*2)<<"\n";
}