#include <iostream>
#include <fstream>
using namespace std;

long long* ciur;
long long n;

void ciurEfectuare(long long k)
{

    for (long long i = 2; (k * i) <= n; i++)
        ciur[k * i] = 1;
}

int main()
{
    ifstream in("ciur.in");
    ofstream out("ciur.out");

    in >> n;

    ciur = new long long[n + 1];

    for (long long i = 0; i <= n; i++)
        ciur[i] = 0;

    for (long long i = 2; i <= n; i++)
        ciurEfectuare(i);

    long long count = 0;

    for (long long i = 2; i <= n; i++)
        if (!ciur[i])
            count++;

    out << count;

    return 0;
}