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;
class Program
{
    public static void Main()
    {
        char[] n = Console.ReadLine().ToCharArray();
        int sum = (int)Char.GetNumericValue(n[0]) - 1;
        sum += 9 * (n.Length - 1);
        bool f = true;
        if (n.Length >= 2)
            for (int i = 1; i < n.Length; i++)
                f = f && (int)Char.GetNumericValue(n[i]) == 9;
        if (f)
            Console.WriteLine(sum + 1);
        else
            Console.WriteLine(sum);
    }
}