#include <bits/stdc++.h>
using namespace std;

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

int n;
bitset<2000005> b;

void Ciur()
{
    b[1] = 1;
    for (int i = 4; i <= n; i += 2)
        b[i] = 1;
    for (int i = 3; i * i <= n; i += 2)
        if (b[i] == 0)
            for (int j = i * i; j <= n; j += 2 * i)
                b[j] = 1;
}

int main()
{
    fin >> n;
    Ciur();
    fout << n - b.count();
    return 0;
}