/* ---------- STL Libraries ---------- */
// IO library
#include <cstdio>
#include <fstream>
#include <iomanip>
#include <ios>
#include <iostream>

// algorithm library
#include <algorithm>
#include <cmath>
#include <numeric>
#include <random>
#include <cstring>

// container library
#include <array>
#include <bitset>
#include <deque>
#include <map>
#include <unordered_map>
#include <queue>
#include <set>
#include <string>
#include <tuple>
#include <vector>
#include <stack>

/* ---------- Namespace ---------- */
using namespace std;

/* ---------- Type ---------- */
using ll = long long;
#define int ll
#define P pair<ll, ll>

/* ---------- Constants  */
const double PI = 3.141592653589793238462643383279;
const ll MOD = 1e9 + 7;
const int INF = 1LL << 55;

/* v-v-v-v-v-v-v-v-v Main Part v-v-v-v-v-v-v-v-v */
signed main() {
    int N;
    cin >> N;

    if (N == 1) {
        cout << 0 << endl;
        return 0;
    }

    vector<bool> visited(N + 1, false);
    vector<int> before;
    vector<int> after;
    for (int i = 1; i < N - i && i + 1 < N - i; i += 2) {
        before.push_back(i);
        before.push_back(N - i);
        visited[i] = true;
        visited[N - i] = true;

        after.push_back(N - i + 1);
        after.push_back(i + 1);
        visited[N - i + 1] = true;
        visited[N - i] = true;
    }

    reverse(after.begin(), after.end());
    for (int i = 1; i <= N; i++) if (!visited[i]) before.push_back(i);

    for (int a : after) before.push_back(a);

    int ret = before[0] * before[before.size() - 1];
    for (int i = 0; i < before.size() - 1; i++) ret += before[i] * before[i+1];

    cout << ret << endl;
    return 0;
}