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 Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.Scanner;

public class Main {

  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    long n = sc.nextLong();
    if (n < 10) {
      System.out.println(n);
      return;
    }

    String s = Long.toString(n);
    long tmp = (long) Math.pow(10, s.length()) - 1;
    long miner = (long) Math.pow(10, s.length() - 1);

    while (true) {
      if (tmp <= n) {
        String o = Long.toString(tmp);
        int a = 0;
        for (int i = 0; i < o.length(); i++) {
          a += Character.getNumericValue(o.charAt(i));
        }
        System.out.println(a);
        return;
      }

      tmp -= miner;
    }

  }
}