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 = sc.nextInt();
      int output = 0;
      for(int i = 1; i <= N; i++){
        String tmp = String.valueOf(i);
        if(tmp.length() % 2 == 1){
          output++;
        }
      }
      System.out.println(output);
	}
}