#include <fstream>
#include <bitset>
#define NMAX 2000050

using namespace std;

ifstream f("ciur.in");
ofstream g("ciur.out");

int n, ans = 1;
bitset < NMAX > v;

void ciur()
{
    for (int i = 4; i <= n; i += 2)
        v[i] = 1;

    for (int i = 3; i <= n; i += 2)
        if (!v[i])
    {
        ans ++;

        for (int j = 3 * i; j <= n; j += 2 * i)
            v[j] = 1;
    }
}

int main()
{
    f >> n;

    ciur();

    g << ans << '\n';
    return 0;
}