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 scn = new Scanner(System.in);
		int N = scn.nextInt();
		int ans = 0;
		int num = 0;
		while(N/(int)Math.pow(10, num) > 0) {
			num++;
		}

		for(int i = 0;i < num-1;i+=2) {
			ans += 9 * Math.pow(10,i);
		}
		if(num%2 == 1) {
			ans += N - Math.pow(10, num-1) + 1;
		}
		System.out.println(ans);
	}

}
