#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 first_number_in_group;
    first_number_in_group=k+((k-1)*(k-1));
    long int sum=0,index=0;
    for(index=0;index<k;index++)
    {
        sum+=first_number_in_group;
        first_number_in_group= first_number_in_group+2;
    }
    
    return sum;
}

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