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;

namespace agc021_a
{
    class Program
    {
        static void Main(string[] args)
        {
            string s = Console.ReadLine();
            int ret = 0;
            int i = 0;
            if (s[0] == '9')
            {
                bool flag = true;
                for (int j = 0; j < s.Length; j++) if (s[j] != '9') flag = false;
                Console.WriteLine(flag ? s.Length * 9 : s.Length * 9 - 1);
            }
            else
            {
                for (; i < s.Length; i++)
                {
                    if (s[i] == '9')
                    {
                        ret += 9;
                    }
                    else
                    {
                        ret += int.Parse(s[i].ToString()) - 1;
                        break;
                    }
                }
                Console.WriteLine((s.Length - i - 1) * 9 + ret);
            }
        }
    }
}