#include <fstream>
#define NMax 2000001
using namespace std;

ifstream fin("ciur.in");
ofstream fout("ciur.out");
char a[NMax];
int n;
short sol;

int main()
{
	int i,j;
	fin>>n;
	
	for (i=2;i<=n/2;i++)
		if (a[i]==0)
			for (j=2*i;j<=n;j=j+i)
				++a[j];
	
	for (i=2;i<=n;i++)
		if (a[i]==0)
			++sol;
	fout<<sol;
	
	fout.close();
	return 0;
}