#include <bits/stdc++.h>

using namespace std;
int main() {
    long long k;
    cin >> k;
    long long a = (long long) (k * (k - 1) / 2);
    long long b = (long long) (k * (k + 1) / 2);
    cout << b * b - a * a << endl;
    return 0;
}