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 N = Integer.parseInt(sc.next());
    int ans = 0;
    for(int i = 1; i <= N; i++){
      if((1 <= i && i < 10) || (100 <= i && i < 1000) || (10000 <= i && i < 100000)){
        ans++;
      }
    }
    System.out.println(ans);
  }
}