#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 st,end,m,n,num;
    num=(k-1)*(k)/2;
    st=2*(num)+1;
    end=((2*st+(k-1)*2)*k)/2;
    
    return end;
    
    // Return the sum of the elements of the k'th group.
}

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