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 static System.Console;
using static System.Math;

class Program
{
    static void Main()
    {
        var N = ReadLine();
        var f = true;
        if (N.Length == 1)
        {
            WriteLine(int.Parse(N));
        }
        for (int i = 1; i < N.Length; i++)
        {
            if (N[i] != '9')
            {
                f = false;
            }
        }
        if (f)
        {
            WriteLine(N.Sum(x => x - '0'));
            return;
        }

        WriteLine((N.Length - 1) * 9 + N[0] - '0' - 1);
    }
}