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 Scala (2.11.7) (judge verdict: Accepted)

import scala.io.{StdIn => in}

object Main extends App {
  val n = in.readLine
  val digit = n.size
  val res = {
    if(n.tail.forall(_ == '9')) n
    else if(n.head == '1') Array.fill(digit-1)(9).mkString
    else (n.head.toString.toInt - 1) + Array.fill(digit-1)(9).mkString
  }
  // println(res)
  val ans = res.map(_.toString.toLong).reduce(_+_)
  println(ans)
}