#include <fstream>
using namespace std;

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

int n, i, j, k, v[2000002];

int main() {
    fin >> n;
    fin.close();
    for (i = 2; i * i <= n; ++i) {
        ++i;
        if (!v[i])
            for (j = i; j <= n; j += i)
                v[j] = 1;
    }
    for (i = 3; i <= n; ++i)
        if (!v[++i])
            ++k;
    fout << k + 1;
    fout.close();
    return 0;
}