//Date: 02-12-17

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<stdbool.h>
#include<float.h>
#include<math.h>
#include<inttypes.h>
#include<assert.h>
#include<ctype.h>
#include<limits.h>
#include<time.h>
#define ll long long
#define For(i,n)	for(i=0;i<n;i++)
#define rep(i ,a ,b)	for(i=(a);i<=(b);i++)
#define mset(a ,value)	memset(a ,value ,sizeof(a))
#define s(a)	scanf("%d" ,&a);
#define ls(a)	scanf("%ld" ,&a)
#define reg(i)	register int i
#define infinite INT_MAX
#define N 100005
#define NIL -1
int min(int a,int b){	return (a < b ? a : b)	;}	
int max(int a,int b){	return (a > b ? a : b)	;}
const int mod = 1e9 + 7;
int main(){
	ll k;
	scanf("%lld" ,&k);
	ll x = k*(k - 1) / 2;
	x++;
	ll s = 2*x - 1 ,ans = 0;
	int i = 0;
	while(i < k){
		i++;
		ans += s;
		s += 2;
	}
	printf("%lld" ,ans);
	return 0;
}