#include <bits/stdc++.h>

using namespace std;

bitset<2000005> ciur;
int N, ans = 0;

void sieve()
{
    for (int i = 3; i <= N; i += 2)
        if (ciur[i] == false) {
            ++ans;
            for (int j = 3; i * j <= N; j += 2)
                ciur[i * j] = true;
        }
}

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

    fin >> N;
    sieve();
    fout << ans + 1;

    return 0;
}