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 ans = 0;

	for(int i=1; i<=N; i++){

	String n = Integer.toString(i);

	if(n.length()%2 == 1){

	ans += 1;

}
}

	System.out.println(ans);

 }
}