#include <cstdio>
#include <iostream>
using namespace std;

int max_area(int n)
{
  if (n == 1){
    return (2);
  }

  return ((n - 1) + n); // before sum area + sum draw line
}

int main()
{
  int n;

  while (~scanf("%d", &n)){
    printf("%d\n", max_area(n));
  }

  return (0);
}