// infoarenaDFSnonRec.cpp : Defines the entry point for the console application.
//

//#include "stdafx.h"
#include <fstream>

#define MaxN 2000005

using namespace std;

ifstream fin("ciur.in");
ofstream fout("ciur.out");

int N;
bool sieve[MaxN];

int main() {
	fin >> N;

	int sqrtN = sqrt(N);
	for (int i = 3; i <= sqrtN; i += 2) {
		for (int j = i + i + i; j <= N; j += i) {
			sieve[j] = true;
		}
	}
	int res = 1;
	for (int i = 3; i <= N; i += 2)
		if (!sieve[i])
			++res;

	fout << res;

	return 0;
}