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;
class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int A = in.nextInt();
        int i = 10, res = 0, sign = 1;
        while (A >= i) {
            res += (i - 1) * sign;
            sign *= -1;
            i *= 10;
        }
        if (res <= 0) res += A;
        System.out.println(res);
    }
}