#define dim1 2000001
#include<fstream>

using namespace std;


int a[dim1];
long n;

void ciuru()
{
	a[0]=a[1]=1;
	for(long p = 2; p < n; p++)
		if(a[p]==0)
			for(long i=2*p;i < dim1; i+=p)
				a[i]=1;
}

void afisare()
{
	ofstream g("ciur.out");
	long   nr = 0;
	for(long i=0; i < n; i++)
		nr += 1 - a[i]; 
	g << nr;
	g.close();
}

void main(){
	ifstream f("ciur.in");
	f >> n;
	ciuru();
	afisare();
	f.close();

}
//---------------------------------------------------------------------------