#include <fstream>
#define fisier "ciur"
std::ifstream in(fisier ".in");
std::ofstream out(fisier ".out");
#include <bitset>
std::bitset<2000003> C;
int main()
{
    int n;
    in >> n;
    for (int i = 2; i <= n; i++)
        if (not C[i])
            for (int j = i << 1; j <= n; j += i)
                C[j] = true;
    out << n - C.count() - 1;
}