#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
#define all(v) begin(v), end(v)
#define al(v, l, r) begin(v) + l, begin(v) + r + 1
#define sz(v) (int)v.size()
#define pb push_back
#define pob pop_back
#define fs first
#define sd second

constexpr int inf = 2e9;
constexpr ll infll = 4e18;
constexpr int N = 2e6 + 5;

int n, ans;
bool c[N];
signed main() {
    ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
    freopen("ciur.in", "r", stdin);
    freopen("ciur.out", "w", stdout);

    c[0] = c[1] = true;
    for (int i = 2; i < N; ++i) {
        if (c[i]) {
            continue;
        }

        if (1ll * i * i >= N) {
            break;
        }

        for (int j = i * i; j < N; j += i) {
            c[j] = true;
        }
    }

    cin >> n;
    for (int i = 1; i <= n; ++i) {
        ans += !c[i];
    }

    cout << ans << "\n";
}