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

long long int sumOfGroup(int k) {
    //long ans;
    //ans = pow(k,3);
    //return ans;
    long long int start= 0;
    for (long int i = k-1; i > 0; i--) {
        start += i;
    }
    start = (2 * start) + 1;
    long long int sum = 0;
    for (long int i = k-1 ; i >=0 ; i--, start +=2) {
        sum += start; 
    }
    return sum;
}

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