#include<fstream.h>
using  namespace std;

int c=1;
ifstream f("ciur.in");
ofstream g("ciur.out");

struct nod{
int info;
nod *ad;}; nod *prim ;

void adaugare(nod *&prim, int x)
{nod *aux;
aux=new nod ;
aux->info=x;
aux->ad=prim;
prim=aux;
}
void find(nod *&prim,int i)
{
 nod *aux;  int z;
z=0;
 for(aux=prim;aux!=0 && z==0;aux=aux->ad)
 if(i%aux->info==0)
  z=1;
  if(z==0) {adaugare (prim,i);
				c++; } }




int main()
{nod *aux;long n;
f>>n;
prim=new nod;
prim->info=2;
prim->ad=0;
for(long i=3;i<=n; i=i+2)
find (prim,i);

g<<c;

return 0;

}