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: Accepted)

using System;

namespace agc021_a
{
    class program
    {
        static void Main(string[] args)
        {
            ChangeLocalDebugInput();

            string str = Console.ReadLine();
            int ans = 0;
            bool allnine = true;
            if (str.Length == 1)
            {
                ans = int.Parse(str);
            } else
            {
                int head = int.Parse(str.Substring(0, 1));
                string rest = str.Substring(1);
                int rest_num = str.Length - 1;
                for (int i = 0; i < rest.Length; i++)
                {
                    if (rest[i] != '9')
                    {
                        allnine = false;
                    }
                }
                if (allnine)
                {
                    ans = head + rest_num * 9;
                } else
                {
                    ans = head - 1 + rest_num * 9;
                }
            }
            Console.WriteLine(ans);
        }


        [System.Diagnostics.Conditional("LOCAL_DEBUG")]
        static void ChangeLocalDebugInput()
        {
            Console.SetIn(new System.IO.StreamReader("../../stdin.txt"));
        }
    }
}