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
import java.util.*;

public class Main
{
	public static void main(String args[])
	{
		Scanner sc=new Scanner(System.in);
		int a,b,c=0;
		a=sc.nextInt();
		for(int i=1;i<=a;i++)
		{
			if(String.valueOf(i).length()%2 != 0)
			{c++;}
		}
		System.out.println(c);
	}
}