#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) {
    // Return the sum of the elements of the k'th group.
    long int sum_sub_1 = 1LL*k*(k-1)/2;
    long int beg = sum_sub_1*2+1;
    // printf("%d %d\n", beg, sum_sub_1);
    return beg*k + sum_sub_1*2;
}

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