#include <bits/stdc++.h>
#define pii pair<int, int>
#define ff first
#define ss second
#define vi vector<int>
#define vvi vector<vi>
#define pb push_back
#define eb emplace_back


using namespace std;
const string TASK("ciur");
ifstream fin(TASK + ".in");
ofstream fout(TASK + ".out");
#define cin fin
#define cout fout

const int N = 2e6 + 9;

int n;

bool p[N];
void Ciur(int n)
{
    p[0] = p[1] = 1;
    for(int i = 2; i <= n; ++i)
        if(!p[i])
            for(int j = 2 * i; j <= n; j += i)
                p[j] = 1;
}

int main()
{
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);

    cin >> n;
    Ciur(n);

    int cnt = 0;
    for(int i = 1; i <= n; ++i)cnt += !p[i];
    cout << cnt << '\n';
    return 0;
}