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 scan = new Scanner(System.in);
        Integer N = Integer.parseInt(scan.next());

        int counter = 0;

        for(int i=1;i<=N;i++){
            if(String.valueOf(i).length() % 2 == 1) counter++;
        }

        System.out.println(counter);

    }
}
