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)

ary = gets.chomp.split('').map(&:to_i)

if ary.size == 1 then
  max = ary[0]
else
  if ary[0] == 9 then
    if ary.sort.uniq[0] == 9 then   # 全て 9                                                     
      max = 9 * (ary.size)
    else
      max = 8 + 9 * (ary.size-1)
    end
  else
    max = (ary[0]-1) + 9 * (ary.size-1)
  end
end

puts max