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 scan = new Scanner(System.in);

		int N = scan.nextInt();

		int count = 0;

		for(int i =1; i < N+1 ; i++) {
			if( String.valueOf(i).length()%2 == 1) {
				count++;
			}
		}
		System.out.println(count);
		scan.close();
	}
}
