#include <iostream>
#include <fstream>
#include <map>
#include <cmath>
#include <math.h>
#include <set>
#include <vector>
#include <sstream>
#include <string>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <queue>
#include <cstdlib>
#include <iomanip>
#include <ctime>
#include <time.h>

typedef long long int ll;
typedef long double ld;
const ll INF = 2e9 + 999, MOD = 1e9 + 7, MAXN = 100001;    // 18
const ld EPS = 0.000001;
#define forn(a, b) for (ll i = a; i < b; i++)
#define fore(p, a, b) for (ll p = a; p < b; p++)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define pb(a) push_back(a)
#define sz(a) (int) a.size()
#define mp(a, b) make_pair(a, b)
#define ft first
#define sd second
#define cotu cout
#define itn ll
#define pll pair<ll, ll>

using namespace std;

int main() {
    ll k;
    cin >> k;
    ll now = ((k - 1) * (k) / 2) * 2 + 1;
    ll ans=0;
    for (int i=0; i<k; ++i) {
        ans += now;
        now += 2;
    }
    cout << ans;
    return 0;
}