#include <iostream>
#include <fstream>

using namespace std;

ifstream f ("12perm.in");
ofstream g ("12perm.out");

const int MOD = 1048576;
const int NMAX = 15000000 + 1;

int n, v[NMAX];

void rezolva () {
    v[1] = 1;
    v[2] = 2;
    v[3] = 6;
    v[4] = 12;
    for (int i = 5; i <= n; i++) v[i] = v[i - 1] + v[i - 3] + 2 * (i - 2);
    g << v[n] << '\n';
}

int main () {
    f >> n;
    rezolva();
    return 0;
}