#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;
}