#include <fstream>

using namespace std;

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

bool v[2000001];
int n, i, j, nrp;

int main()
{
    f >> n;
    nrp = 1;
    for (i = 1; 2*i*(i+1) <= n; i++)
        if (v[i] == 0)
            for (j = 2*i*(i+1); 2*j+1 <= n; j += 2*i+1)
                v[j] = 1;

    for (i = 1; 2*i+1 <= n; i++)
        nrp += (1-v[i]);
    g << nrp;
    return 0;
}