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

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

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