#include <iostream>
#include <cstring>
#include <vector>
#include <set>
#include <list>
#include <map>
#include <deque>
#include <unordered_map>
#include <algorithm>
#include <utility>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<ll> vll;
#define for1(i,n) for (ll i=0;i<(n);i++)
#define for2(i,m,n) for (ll i=(m);i<(n);i++)
#define for3(i,m,n,d) for (ll i=(m);i<(n);i+=(d))
#define DEBUG 0
template <class T>
void dumplist(T list)
{
    for (auto item : list) {
        cout << item << " ";
    }
    cout << endl;
}

void solve()
{
    ll N;
    cin >> N;
    if (N == 1) {
        cout << 0 << endl;
        return;
    }
    deque<ll> q;
    q.push_back(1);
    ll s = 2;
    ll l = N;
    ll ans = 0;
    while(s < l) {
        if (s == l) {
            q.push_back(l);
            --l;
            break;
        } else {
            q.push_front(l);
            --l;
            q.push_back(l);
            --l;
            if (s > l) break;
        }

        if (s == l) {
            q.push_back(s);
            ++s;
            break;
        } else {
            q.push_front(s);
            ++s;
            q.push_back(s);
            ++s;
            if (s > l) break;
        }
    }

    ll pre = q.back();
    //dumplist(q);
    for (ll a : q) {
        if (pre == 0) {
            pre = a;
        }
        else {
            ans += (pre * a) + (a - pre);
            pre = a;
        }
    }
    cout << ans << endl;
}

int main()
{
    do {
        solve();
    } while (DEBUG);
}