#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pii> vii;
#define GCD(a,b) __gcd(a, b)
#define mp make_pair
#define DEBUG(x) cout << x << endl
#define ALL(x) x.begin(), x.end()
#define INF 2147483646
#define pb push_back
#define lend '\n'
#define MAX_ 200100



ll sumFirstOdd(ll n) {
    return n * n;
}
int main() {
    ios_base::sync_with_stdio(false);
    ll k; cin >> k;
    ll idx = k * (k + 1) / 2;
    
    ll ans = sumFirstOdd(idx) - sumFirstOdd(idx - k);
    cout << ans << lend;
}