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

object Main {

  def digitSum(n: String): Int = n.toList.map(_.asDigit).sum

  def main(args: Array[String]): Unit = {
    val N: Long = StdIn.readLine.toLong
    val s: String = (N+1).toString
    println(digitSum((s(0).asDigit-1).toString + "9" * (s.length-1)))
  }
}