#include <fstream>
using namespace std;

char M[2000005] = {0};

int main(void)
{
 fstream fin("ciur.in",ios::in);
 fstream fout("ciur.out",ios::out);
 long N,i,j;
 fin >> N;
 for (i = 2;i <= N;i += 1)
  {
   if (M[i] == 0)
     {
      for (j = (i << 1);j <= N;j += i)
       {
        M[j] = 1;
       }
     }
  }
 j = 0;
 for (i = 2;i <= N;i += 1)
  {
   j += M[i] - 1;
  }
 fout << -j;
 fin.close();
 fout.close();
 return 0;
}