#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

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

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