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 stdIn=new Scanner(System.in);
		int N=stdIn.nextInt();
		int ans=0,x=1;
		while(x<=N){
			String a=String.valueOf(x);
			if(a.length()%2==1)
				ans++;
			x++;
		}
		System.out.println(ans);
	}
}