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 val1 = sc.nextInt();

        int count = 0;
        for (int i = 1; i <= val1; i++) {
            String temp = "" + i;
            if ((temp.length() % 2) != 0) {
                count++;
            }
        }
        System.out.println(count);
    }
}