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;
		for(int i = 1; i < N + 1; i++){
			if(i < 10){
				ans++;
			}
			if(100 <= i && i < 1000){
				ans++;
			}
			if(10000 <= i && i < 100000){
				ans++;
			}
		}
		System.out.println(ans);
		stdIn.close();
	}
}
