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 s = new Scanner(System.in);

      	int sc = s.nextInt();

        int judge = 0;
        for (int i = 1; i < sc+1; i++) {
            if((String.valueOf( i ).length())%2 ==1){
                judge++;
            }
        }
        System.out.println(judge);

    }
}