#include<fstream.h>

 unsigned long int n,p,y[100];

 int main()

  {ifstream fin("fractii.in");
   ofstream fout("fractii.out");

   fin>>n;
    if(n>2) y[++ p]=n*2+3;
     else if(n==2) y[++p]=n*2+1;

      else if(n==1) y[++p]=1;
    fout<<y[p];

   fin.close();
   fout.close();
  }