#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;
    long int j, p, sum, start;
    p = (long int) k;
    start = (long int) (p * (p - 1) + 1);

    for (i = 1; i <= k; ++i)
    {
        sum += start;
        start += 2;
    }
    return sum;   
}

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