#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 int k) {
    // Return the sum of the elements of the k'th group.
    long int sum=0;
    long int i;
    for(i=0;i<k;i++)
    {
        sum=sum+(k*(k-1)+1+2*i);
    }
    return sum;
}

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