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

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