#include <iostream>
#include <fstream>

using namespace std;

ifstream intrare("fractii.in");

ofstream iesire("fractii.out");

long long int i,n,nr,c,j;
bool adun=true;
int main()
{
    intrare>>n;
    nr=n*n;
    nr-=n-1;

    for(i=2;i<=n/2;i++){
         adun=true;
         c=(n/i);
    if(i%2==0 && i!=2)
            adun=false;

          if(i%2!=0)
                for(j=3;j*j<=i;j+=2)
                    if(i%j==0)
          {
              adun=false;
              break;
          }


        if(adun==true){
            nr-=c*c-c;

        }


    }
    iesire<<nr;




    return 0;
}