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 res = 0;

		//　桁数が奇数の数を数える
		for(int i = 1; i <= n; i++) {
			if(Integer.toString(i).length() % 2 == 1) {
				res++;
			}
		}
		
		System.out.println(res);
		sc.close();
	}
}