/**
**	author: Mathura
**	date  : 03.12.2017
**/
#include <bits/stdc++.h>
using namespace std;
#define ull unsigned long long int
int main(){
	ull k;
	cin >> k;
	if(k == 1){
	 	cout << 1 << endl;
	 	exit(1);
	}
	ull f = 1;
	ull add = 1;
	ull times = k;
	k--;
	while(k--){
		f = f + add*2;
		add++;
	}
	unsigned long long sum = 0;
	for(ull i = 0; i < times; i++){
		sum += f;
		f += 2;	 	
	}
	cout << sum << endl;
 	return 0;
}