#include <iostream>
#include <fstream>
using namespace std;

int cauta(int numar, int n, int *p) {
  int i,j, nr = 0;
  for(i = 2; i<=n; i++)
    if(n%i == 0)
      for (j = i  ; j <= numar; j = j + i)
        p[j] = 1;

  for (j = 2; j <= numar; j++) {
    if (p[j] == 0) {
      nr++;
    }
    else{
        p[j]=0;
    }
  }

  return nr;
}


int main()
{
    ifstream in;
    in.open("fractii.in");
    ofstream out;
    out.open("fractii.out");
    int nr,suma;
    in >> nr;
    suma = nr+nr-1;
    int *p = new int[nr+1];
    for (int i = 2 ; i <= nr ; i++){
        suma += cauta (nr,i,p);
    }
    out << suma << endl;
    return 0;
}