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 agc021a
{
    class Program
    {
        static void Main(string[] args)
        {
            var N = Console.ReadLine();
            var ret = int.Parse(N[0].ToString()) + 9 * (N.Length -1);
            //文字列Nの最上位の桁(0番目)以降の中から9を削除した時のNの長さが0以外の時
            //入力値Nから最上位の桁を1引いて他の桁を9にした値の桁の和が最大
            if(N.Substring(1).Replace("9","").Length != 0) ret -= 1;
            Console.WriteLine(ret);
            //Console.WriteLine(N.Substring(1).Replace("9",""));
        }
    }
}