Score : 200 points
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).
Input is given from Standard Input in the following format:
N
Print the number of positive integers less than or equal to N that have an odd number of digits.
11
9
Among the positive integers less than or equal to 11, nine integers have an odd number of digits: 1, 2, \ldots, 9.
136
46
In addition to 1, 2, \ldots, 9, another 37 integers also have an odd number of digits: 100, 101, \ldots, 136.
100000
90909