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);
		// 整数の入力
		long n = sc.nextLong();
      
      long cnt = 0;
      String s;
      for(long i = 1; i <= n; i++) {
        s = Long.toString(i);
        if(s.length() % 2 == 1) {
          cnt++;
        }
      }
      System.out.println(cnt);


    }
}
