#include <iostream>
#include <fstream>

using namespace std;

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

int main()
{
    int n,i,ct=0,total=0;
    fin>>n;
    ct=n;
    for(i=2;i<=n;i++)
    {
        if(i%2==0)
        {
            total=total+n/2;
        }
        else
        {
            if(n%2==0)
            {
                total=total+n/2+2;
            }
            else
            {
                total=total+n/2+3;
            }
        }
    }
    fout<<total+ct;
    return 0;
}