#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,m,n) for(int i=m; i<n; ++i)

int main(){
    vector<ll> vec;
    
    for(ll i=1; i<=100000; ++i){
        string s = to_string(i);
        string t = s + s + s;
        vec.push_back(stoll(t));
    }
    
    ll N;
    cin >> N;
    
    auto itr = upper_bound(vec.begin(), vec.end(), N);
    cout << int(itr - vec.begin()) << endl;
    
    return 0;
}