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; 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); } } }