#include <fstream>
#include <algorithm>
#include <bitset>
#define mil 1000000
using namespace std;

const string name("ciur");
ifstream cin(name + ".in");
ofstream cout(name + ".out");

int n, rez = 1;
bitset<2 * mil + 5>E;

void ciur(){
    for(int i = 2; i * i <= n; ++i)
        for(int j = 2; i * j <= n; ++j)
            E[i * j] = 1;
    for(int i = 3; i <= n; i += 2)
        if(!E[i])
            ++rez;
    cout << rez;
}

int main(){

    cin >> n;
    ciur();

    return 0;
}