Problem:
Score : 300 points

Problem Statement

Find the maximum possible sum of the digits (in base 10) of a positive integer not greater than N.

Constraints

1\leq N \leq 10^{16}

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the maximum possible sum of the digits (in base 10) of a positive integer not greater than N.

Sample Input 1

100

Sample Output 1

18

For example, the sum of the digits in 99 is 18, which turns out to be the maximum value.

Sample Input 2

9995

Sample Output 2

35

For example, the sum of the digits in 9989 is 35, which turns out to be the maximum value.

Sample Input 3

3141592653589793

Sample Output 3

137

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.IO;
using static System.Console;

class Program
{
    static void Main()
    {
        var N = ReadLine();
        if (N.Length == 1) WriteLine(N);
        else if (N.Count(x => x == '9') == N.Length) WriteLine(N.Select(x => int.Parse(x + "")).Sum());
        else if (N.First() == '1' && N.Count(x => x == '9') == N.Length - 1) WriteLine(N);
        else
        {

            WriteLine(((int.Parse(N.First() + "") - 1).ToString() + "99999999999999999999999999999999999999999999".Substring(0, N.Length - 1)).Select(x => long.Parse(x + "")).Sum());
        }
    }
}