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

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