#include <fstream>

#define Nmax 2000100

using namespace std;

int N, Answer;
bool seen[Nmax];

void Sieve() {

    int i, j;

    Answer += 1;

    for(i = 3; i <= N; i += 2)
        if(!seen[i]) {
            Answer++;

            if(i < 2015)
            for(j = i * i; j <= N; j += (i << 1))
                seen[j] = true;

        }
}
void Read() {

    ifstream in("ciur.in");
    in >> N;
    in.close();
}
void Write() {

    ofstream out("ciur.out");
    out << Answer << '\n';
    out.close();
}
int main() {

    Read();
    Sieve();
    Write();

    return 0;
}