#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) {
    long int n = 0, i, sum = 0, j;
    for(i = 1; i < k; i++)
        n += i;
    //printf("%ld", n);
    for(i = (n*2)+1, j = 0; j < k; j++, i += 2)
        sum += i;
    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;
}