#include <iostream>
#include <fstream>

bool v[2000001];

int main() {
    std::ifstream fin("ciur.in");
    std::ofstream fout("ciur.out");
    int nrNeprime = 0, n;
    fin >> n;
    for(int i = 2; i * i <= n; ++i) {
        if(!v[i]) {
            for (int j = i * i; j <= n; j += i) {
                if(!v[j]){
                    nrNeprime++;
                }
                v[j] = true;
            }
        }
    }

    fout << n - nrNeprime - 1;

    fin.close();
    fout.close();
    return 0;
}