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;
public class Hello{
    public static void Main(){
        var N = long.Parse(Console.ReadLine());
        N = N - (N % 10 + 1);
        Console.WriteLine(SumDigit(N));
        
    }
    static long SumDigit(long n){
        long ans = 0;
        while(n > 0){
            ans += n % 10;
            n /= 10;
        }
        return ans;
    }
}