output_description: Print the maximum possible sum of the digits (in base 10) of a positive
  integer not greater than N.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
attempt: -*- coding: utf-8 -*-
  N = input()
  
  if len(N) == 1:
    # 1桁の数字
    print(N)
  elif all(map(lambda x: x == '9', N[1:])):
    # 下位が全部9の場合
    print(sum(int(n) for n in N))
  else:
    # 下位を全部9にする例
      print(9 * (len(N) - 1) + int(N[0]) - 1)
   
problem_description: Statement
  
  Find the maximum possible sum of the digits (in base 10) of a positive integer
  not greater than N.
samples: [{"input": "100", "output": "18\n    \n\nFor example, the sum of the digits in 99 is 18, which turns out to be the\nmaximum value.\n\n* * *"}, {"input": "9995", "output": "35\n    \n\nFor example, the sum of the digits in 9989 is 35, which turns out to be the\nmaximum value.\n\n* * *"}, {"input": "3141592653589793", "output": "137"}]