#include <bits/stdc++.h>
using namespace std;

#define pb push_back
using ll = long long;

const string fn = "ciur";


ifstream fin(fn + ".in");
ofstream fout(fn + ".out");

int n, ans;
bitset<2000005> prim;
void ciur() {

    prim[0] = prim[1] = 1;
    for (int i = 4; i <= n; i += 2)
        prim[i] = true;

    for (int i = 3; i * i <= n; i += 2) {
        if (!prim[i])
            for (int j = i * i; j <= n; j += i + i)
                prim[j] = true;
    }
    prim.flip();
    for (int i = 2; i <= n; ++i)
        ans += prim[i];
}

int main() {

    fin >> n;
    ciur();
    cout << n;
    fout << ans << '\n';
    fin.close();
    fout.close();
    return 0;
}