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

using namespace std;
int numitor,numarator=1,nr_fractii,n;
int main()
{
    cin>>n;
    nr_fractii=n;
   /*for(int i=1;i<=n;i++)
        cout<<"1/"<<i<<" ";
    cout<<endl;
    nr_fractii=n;
    numarator++;
   while(numarator<=n)
   {
        numitor=1;
        cout<<numarator<<"/"<<numitor<<" ";
        nr_fractii++;
       if(numarator%2==0)
       {
           while(numitor<=n-2 && numitor!=numarator)
           {
               numitor+=2;
               cout<<numarator<<"/"<<numitor<<" ";
               nr_fractii++;
           }
           cout<<endl;
       }
       else
       {
           numitor++;
           while(numitor<=n && numitor!=numarator)
           {
               cout<<numarator<<"/"<<numitor<<" ";
               numitor+=2;
               nr_fractii++;
           }
           cout<<endl;
       }
       numarator++;
   }
   cout<<nr_fractii; */
   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;
       }
   }
   cout<<nr_fractii;
}