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: n = int(input())
  m = n
  k = 0
  while m > 0:
      k += 1
      m = m // 10
  if (n + 1) % (10 ** (k - 1)) == 0:
      print(n // (10 ** (k - 1)) + 9 * (k - 1))
  else:
      print(n // (10 ** (k - 1)) - 1 + 9 * (k - 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"}]