#include<bits/stdc++.h>
using namespace std;
#define mod 1000000007
#define inf 1e15
#define pb push_back
#define mp make_pair
#define Int long long
#define fs first
#define sc second
#define pll pair<Int,Int>
#define pii pair<int,int>
#define piiii pair<pii, pii>
#define MAX 100005
#define LOGN 20
#define gcd __gcd
#define swap(x,y) x^=y^=x^=y
#define optimise_stuff ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
Int modpow(Int a,Int b,Int m){Int c=1;while(b){if(b&1)c=(c*a)%m;b/=2;a=(a*a)%m;}return c;}



int main(){

	Int k, ans = 0, n;

	cin>>k;

	n = (k*(k-1)) + 1;

	for(int i = 0; i < k; i++, n+= 2)
		ans += n;

	cout<<ans<<endl;
	return 0;
}