#include <bits/stdc++.h>

using namespace std;

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

int n;
bool sieve[2000005];

int main()
{
    in >> n;
    for (int i = 4; i <= n; i += 2)
        sieve[i] = true;
    for (int i = 3; i * i <= n; i += 2)
        if (!sieve[i])
            for (int j = i * i; j <= n; j += 2 * i)
                sieve[j] = true;
    int nrp = 0;
    for (int i = 3; i <= n; i += 2)
        if (!sieve[i])
            nrp++;
    out << nrp + 1;
    return 0;
}