#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 int k) {
    long int sum=0;
    long int n=(k*(k-1)/2)+1;
    
    for(long int i=0;i<k;i++)
    {
    
        sum=sum+(2*n-1);
        n++;
    }
    // Return the sum of the elements of the k'th group.
    return sum;
}

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