#include <bits/stdc++.h>
using namespace std;
const int N = 10e6+100;
int cal[N];
int cnt = 0;
void precal(){
   cal[0] = 1;
   int t = 1;
   for (int i = 1; i <= N; i ++){
   		cal[i] = 2*t+1;
   		t++;
   }
}
int main(){
	precal();
	long k; cin >> k;
	long L = pow(k,2) - (k-1);
	long R = pow(k,2) + (k-1);
	//cerr << L << " " << R; 
	long ans = 0;
	for (int i = 1; i <= k; i ++){
		ans += L;
		L += 2;
	}
	cout << ans << endl;
return 0;
}