#include <iostream>
#include <fstream>
#include <cstdlib>
#include <vector>
#include <queue>

using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");

#define ll long long
#define pb push_back
const int NMax = 2e6 + 5;
const ll inf = 1e9 + 5;

int N;
bool notPrime[NMax];

int main() {
    in>>N;

    int ans = 1;
    for (int i=3;i <= N;i += 2) {
        if (notPrime[i]) {
            continue;
        }

        ++ans;
        for (int j=3*i;j <= N;j += 2*i) {
            notPrime[j] = true;
        }
    }
    out<<ans<<'\n';

    in.close();out.close();
    return 0;
}