//@author KhaledAlam.net
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef stringstream ss;
typedef pair<int, int> pii;
//#########################
#define fi           first
#define se           second
#define pb           push_back
#define mp           make_pair
#define out(x)       return cout<<x,0
#define all(x)       x.begin(),x.end()
#define sz(x)        ((int)(x.size()))
#define clr(x)       memset(x,0,sizeof x)
#define rep(i,n)     for(int i=0;i<n;i++)
#define debug(x)     cerr<<"[l#: "<<__LINE__<<"] "<<#x<<" = "<<x<<endl
// v0.0.2 | Github.com/khaledalam/templates/tree/master/cpp
//##########################################################################

#define maxn 10010

int main()
{
//	ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
//	freopen("input.txt", "r", stdin); //freopen("output.txt","w",stdout);

	ll k, sum = 0,prevn=0;
	cin >> k;
	for (int i = 1; i < k; ++i) {
		prevn += i;
	}
	prevn*=2;
	prevn++;
	for (int i = 0; i < k; ++i) {
//		cout<<prevn<<" "<<sum<<endl;
		sum += prevn;
		prevn+=2;
	}
	cout<<sum;
}