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

long int sumOfGroup(long k) {
    // Return the sum of the elements of the k'th group.
    long sum,i,sum_next,sum_prev;
    sum=(k*k)-(k-1);
    sum_next=sum;
    for(i=1;i<k;i++)
    {
       sum_prev=sum;
       sum_next+=2;
       sum=sum_prev+sum_next; 
    }
    return sum;
}

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