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

public class Main {

    public static void main(String[] args) {

        java.util.Scanner sc = new java.util.Scanner(System.in);

        int n = sc.nextInt();

        int count = 0;

        for (int i = 1; i <= n; i++) {
            if (("" + i).length() % 2 == 1) {
                count++;
            }
        }

        System.out.println(count);

    }

}
