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;

public class Main {

	public static void main(String[] args) {
		 Scanner sc = new Scanner(System.in);
		 int N = sc.nextInt();
		 int count = 0;
		 for(int i=1; i<=N; i++) {
			 if((String.valueOf(i).length()) %2 == 1) {
				 count++;
			 }
		 }
		 System.out.println(count);
	}
}