#include <bits/stdc++.h>
using namespace std;

#ifdef DEBUG
#include "../include/debug.hpp"
#else
#define debug(...) 42
#define rdfile(...) 42
#endif

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);

    long long N;
    cin >> N;
    cout << (N == 1 ? 0 : (N*N*N + 3*N*N + 5*N - 6 + (N%2)*3) / 6) << endl;

    return 0;
}