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.io.*;
import java.util.*;

public class Main
{
	public static void main(String []args)throws IOException
	{
		BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
		int n=Integer.parseInt(br.readLine());
		int c=0;
		for(int i=1;i<=n;i++)
		{
			if((((int)Math.log10(i)+1) & 1) == 1)
				++c;
		}
		
		System.out.println(c);		
	}
}


