output_description: Print the number of positive integers less than or equal to N that have an odd
  number of digits.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N
attempt: N = int(input())
  S = 0
  for x in range(1, N + 1):
      i = 0
      j = 0
      XX = x
      while i == 0:
          XX = XX // 10
          if XX == 0:
              i = 1
          j = j + 1
      if j % 2 == 1:
          S = S + 1
  print(S)
  
problem_description: Statement
  
  Given is an integer N. Find the number of positive integers less than or equal
  to N that have an odd number of digits (in base ten without leading zeros).
samples: [{"input": "11", "output": "9\n    \n\nAmong the positive integers less than or equal to 11, nine integers have an\nodd number of digits: 1, 2, \\ldots, 9.\n\n* * *"}, {"input": "136", "output": "46\n    \n\nIn addition to 1, 2, \\ldots, 9, another 37 integers also have an odd number of\ndigits: 100, 101, \\ldots, 136.\n\n* * *"}, {"input": "100000", "output": "90909"}]