#include<bits/stdc++.h>

using namespace std;

#define endl '\n'

typedef long long ll;
typedef pair<int, int> pii;

const int N = 1e6+100;
const int MOD = 1e9 + 7;


int k;

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

	cin >> k;
	ll cnt = 1LL * k * (k + 1) / 2;
	cout << (cnt * cnt - (cnt-k) * (cnt-k)) << endl;
	return 0;
}