#include <fstream>

using namespace std;

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

bool checkPrime(int val)
{
    int check = 0;
    for(int i = 2; i <= val/2; i++)
        if(val % i) check = 0;
        else {
            check = 1;
            break;
        }

    if(check) return false;
    else return true;
}

int main()
{
    int N; fin >> N;
    int cnt = 0;

    for(int i = 2; i <= N; i++)
        if(checkPrime(i)) cnt++;

    fout << cnt;

    return 0;
}