//#include "pch.h"
#include <iostream>
#include <vector>
#include <fstream>
#include <algorithm>
#define nmax 2000005
using namespace std;
ifstream f("ciur.in");
ofstream o("ciur.out");

bool v[2000005];
int n;

void ciur()
{
	for (size_t i = 2; i < nmax; i++)
	{
		for (size_t j = 2 * i; j < nmax; j += i)
		{
			v[j] = true;
		}
	}
}

int main()
{
	ciur();
	f >> n;
	int cite = 0;
	for (size_t i = 2; i <= n; i++)
	{
		if (v[i] == false)
		{
			cite++;
		}
	}
	o << cite;


}