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.*;
class Main{
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int N = sc.nextInt();
    int count = 0;
    for(int i = 1; i <= N; i++) {
      int test = i;
      int num = 0;
      while( test > 0 ) {
        test /= 10;
        num++;
      }
      if( num % 2 != 0 ){
        count++;
      }
    }
    System.out.println(count);
  }
}
