#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

long int sumOfGroup(int k) 
{
    int i, term = -1, sum = 0; 
   for(i = 1; i < k ; i++)
   {
       for(int j = 1; j <= i ; j++)
           term = term + 2;
   }
       if(i == k)
       {
           for(int m = 1; m <= k; m++)
           {
               term = term + 2;
               sum = sum + term;
           }
       }
           return sum;     // Return the sum of the elements of the k'th group.
}

int main() {
    int k; 
    scanf("%i", &k);
    long int answer = sumOfGroup(k);
    printf("%ld\n", answer);
    return 0;
}