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();
		System.out.println(search(N));
	}

	public static int search(int N) {
		int ans = 0;

		for(int n = 1; n <= N; n++) {
			if (Integer.toString(n).length() % 2 == 0) continue;
			ans++;
		}
		return ans;
	}
}
