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 i = 0;
		int j = 0;
		int count = 0;
		String digital;
		
		for(i=1; i <= N; i++){
			digital = String.valueOf(i);
			j = digital.length();
			if(j%2 != 0){
				count++;
			}
		}
		System.out.println(count);
	}
}