#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(long long int k) {
    // Return the sum of the elements of the k'th group.
    long long int p,ans;
    p=(k*(k-1))/2;
    ans=k*((2*p)+k);
    return ans;
}

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