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 Ruby (2.3.3) (judge verdict: Wrong Answer)

num = gets.to_s
sum = 0
j = 0
num.chars do |i|
  if i == 9
    sum += 9
    j += 1
  else
    sum += i.to_i - 1
    j += 1
    break
  end
end
sum += ( num.length - j ) * 9
if num.length == 1
  puts sum.to_i
elsif num[j..-1].length < (num[j..-1].to_i + 1).to_s.length
  puts (sum + 1)
else
  puts sum
end