#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) ;
long int total(int n);
int main() {
    int k; 
    scanf("%i", &k);
    long int answer = sumOfGroup(k);
    printf("%ld\n", answer);
    return 0;
}
long int sumOfGroup(int k) {
  long int last = 2*total(k)-1;
    int count =0;
    long int sum=0;
    for(long int i =last;;i -=2)
    {count++;
    if(count==k+1)break;
     sum +=i;
     
    }
    return sum;
    // Return the sum of the elements of the k'th group.
}
long int total(int n){
  long int s =0;
    
    for(int i=n;i>0;i--)
    {s +=i;}
    return s;
}