// Template
#include <bits/stdc++.h>
#define rep_override(x, y, z, name, ...) name
#define rep2(i, n) for (int i = 0; i < (n); ++i)
#define rep3(i, l, r) for (int i = (l); i < (r); ++i)
#define rep(...) rep_override(__VA_ARGS__, rep3, rep2)(__VA_ARGS__)
#define per(i, n) for (int i = (n) - 1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()
using namespace std;
using ll = long long;
constexpr int inf = 1001001001;
constexpr ll INF = 3003003003003003003;
template <typename T> inline bool chmin(T& x, const T& y) {if (x > y) {x = y; return 1;} return 0;}
template <typename T> inline bool chmax(T& x, const T& y) {if (x < y) {x = y; return 1;} return 0;}
struct IOSET {IOSET() {cin.tie(0); ios::sync_with_stdio(0); cout << fixed << setprecision(10);}} ioset;

// Main
int main() {
    int n;
    cin >> n;
    
    if (n < 100) {
        cout << n / 3 - 3 << "\n";
        return 0;
    }
    if (n < 300) {
        cout << 30 << "\n";
        return 0;
    }
    int ans = 30;
    ll now = 300;
    while (true) {
        ++ans;
        ll d = 1;
        while (true) {
            d *= 10;
            if (now % d != d - 1) {
                ++now;
                now += d / 10 * 2;
                break;
            }
        }
        if (now > n) break;
    }
    cout << ans << "\n";
    return 0;
}