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)

n=gets.chomp.split("").map(&:to_i)
sum=0
flag1=false
j=0
if n[0]==1
  n.each do |i|
    sum+=9
    flag1=true if i!=9 && j!=0
    j+=1
  end
  puts sum-9 if flag1==true
  puts sum if flag1!=true
end
flag=false

if n[0]==9
  n.each do |i|
    sum+=9
    if i!=9 && flag==false
      sum+=8
      flag=true
    end
  end
  puts sum-9
end

if n[0]!=9 && n[0]!=1
  sum+=n[0]
  n.each do |i|
    sum+=9
  end
  puts sum-10
end