// __author__ HD

#include <bits/stdc++.h>

#define endl '\n'
#define MAX 20
#define MOD 1000000009
using namespace std;

typedef long long ll;

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

    //Solve....

    ll k;
    cin >> k;

    ll n = (k * (k-1))/2ll;
    cout << (n+k)*(n+k) - n*n << endl;
    return 0;
}