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.*;

	public class Main {

		public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
        int sum = 0;
        for (int i = 1; i <= a; i++) {
          if(!(String.valueOf(i).length()%2==0)){
            sum++;
          }
        }
          System.out.println(sum);
	}
}