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();
      String s;
      int count = 0;

      for (int i = 1;i<=a ;i++ ) {
        s = String.valueOf(i);
        if(s.length()%2==0){
          count++;
        }
      }
      System.out.println(a-count);
}
}
