using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Globalization;
using System.Diagnostics;
using static System.Console;
using Pair = System.Collections.Generic.KeyValuePair<int, int>;

class Program
{
    static void Main()
    {
        SetOut(new StreamWriter(OpenStandardOutput()) { AutoFlush = false });
        //SetOut(new StreamWriter("out.txt"));
        new Program().Solve();
        Out.Flush();
    }
    Scanner cin = new Scanner();
    Random rnd = new Random();
    Stopwatch sw = new Stopwatch();
    readonly int[] dd = { 0, 1, 0, -1, 0 };
    readonly int mod = 1000000007;
    readonly string alfa = "abcdefghijklmnopqrstuvwxyz";
    int Z = 1000000001;

    void Solve()
    {
        long N = cin.Nextlong;
        long ans = 0;
        long p = 0;
        int d = 1; // 桁数
        for (long i = Z; i <= N;)
        {
            //WriteLine(i);
            long J = Math.Min(9, N / i);
            if (d == 1) ans += J;
            else if (d % 2 == 0) ans += (long)Math.Pow(J, d / 2);
            else ans += 9 * (long)Math.Pow(J, d / 2);
            //Console.WriteLine(J + " " + d + " " + (ans - p));
            p = ans;
            d++;
            long cnt = i;
            int x = cnt.ToString().Length;
            while (i.ToString().Length == x)
            {
                i += cnt;
            }
            i -= cnt;
            while (i.ToString().Length == x)
            {
                i += Z;
            }
            i += Z;
        }
        WriteLine(ans);
    }

}

class Scanner
{
    string[] s; int i;
    char[] cs = new char[] { ' ' };
    public Scanner() { s = new string[0]; i = 0; }
    public string[] Scan { get { return ReadLine().Split(); } }
    public int[] Scanint { get { return Array.ConvertAll(Scan, int.Parse); } }
    public long[] Scanlong { get { return Array.ConvertAll(Scan, long.Parse); } }
    public double[] Scandouble { get { return Array.ConvertAll(Scan, double.Parse); } }
    public string Next
    {
        get
        {
            if (i < s.Length) return s[i++];
            string st = ReadLine();
            while (st == "") st = ReadLine();
            s = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            i = 0;
            return Next;
        }
    }
    public int Nextint { get { return int.Parse(Next); } }
    public long Nextlong { get { return long.Parse(Next); } }
    public double Nextdouble { get { return double.Parse(Next); } }
}