#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 a = 2 * (k * (k - 1LL) /  2) + 1;
  long int s = 0;
  for (int i = 0; i < k; i++, a += 2) {
    s += a;
  }
  return s;
}

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