#include <fstream>
#include <bitset>

std::ifstream fin("ciur.in");
std::ofstream fout("ciur.out");

std::bitset<2000001> ciur;
size_t N, ans{0};

int main()
{
    fin >> N;

    for(size_t i = 2; i <= 1414; i++){
        if(!ciur.test(i)){

            for(size_t j = i * i; j < 2000001; j += i) ciur.set(j, 1);
        }
    }

    for(size_t i = 2; i <= N; i++)
    {
        if(!ciur.test(i)) ans++;
    }

    fout << ans;
}