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)

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