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).

Constraints

• $1 \leq N \leq 10^5$

Input

Input is given from Standard Input in the following format:

N

Output

Print the number of positive integers less than or equal to N that have an odd number of digits.

Examples

Input

11

Output

9

Input

136

Output

46

Input

100000

Output

90909

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