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;
using System.Linq;
using System.Collections.Generic;
class P
{
    static void Main()
    {
        string n = long.Parse(Console.ReadLine()).ToString();
        int res = 0;
        if (n.Length == 1)
        {
            res = n[0] - '0';
        }
        else if (n[0] != '9')
        {
            if (n.Count(x => x != '9') == 1)
            {
                res = 9 * (n.Length - 1) + (n[0] - '0');
            }
            else
            {
                res = 9 * (n.Length - 1) + (n[0] - '0' - 1);
            }
        }
        else if (n.Count(x => x != '9') != 0)
        {
            res = 9 * (n.Length - 1) + 8;
        }
        else
        {
            res = 9 * (n.Length - 1) + 9;
        }
        Console.WriteLine(res);
    }
}