#include <iostream>
#include<bits/stdc++.h>

using namespace std;
int numitor,numarator=1,nr_fractii,n;
int main()
{
    ifstream f("fractii.in");
    ofstream g("fractiii.out");
    f>>n;
    nr_fractii=n;
   if(n%2==0)
   {
        for(int i=2;i<=n;i++)
   {
       if(i%2==0)
        nr_fractii+=n/2;
       else  nr_fractii+=n/2+1;
   }
   }
   else
   {
       for(int i=2;i<=n;i++)
       {
           nr_fractii+=(n+1)/2;
       }
   }
   g<<nr_fractii;
}