#include<fstream>
using namespace std;

int main(){
	ifstream fin ("ciur.in");
	ofstream fout ("ciur.out");
	int i, j, N;
	fin >> N;
	char v[N+1]; 
	
	for (i = 1; i <= N; i++) v[i] = 1;
	for (i = 3; i <= N; i+=2)
		for (j = 2*i; j <= N ; j+=i) v[j] = 0;
	
	int nr = 1;
	for (i = 2; i <= N; i++) 
		if (v[i] == 1 && i%2 == 1) nr++;
	
	fout<<nr<<"\n";
	fout.close();
	return 0;
}