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 in = new Scanner(System.in);
		int n = in.nextInt();
		int ans = 0;
		if(n<10) ans = n;
		else if(n<100) ans = 9;
		else if(n<1000) ans = 9 + n - 99;
		else if(n<10000) ans = 909;
		else if(n<100000) ans = 909 + n - 9999;
		else if(n<1000000) ans = 90909;
		System.out.println(ans);
		in.close();

	}

}
