#include <bits/stdc++.h>
#define N_MAX 2000005

using namespace std;

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

int N, Ans;
bitset < N_MAX > prime;

int main()
{
    fin >> N;
    prime[0] = prime[1] = 1;
    for (int i = 1; i * i <= N; i++)
        if (prime[i] == 0)
            for (int j = i * i; j <= N; j += i)
                prime[j] = 1;

    for (int i = 1; i <= N; i++)
        Ans += 1 - prime[i];

    fout << Ans << "\n";
    return 0;
}