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.Scanner;

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

	  System.out.println(count);
  }
}
