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.Scanner;
public class Main {

	public static void main(String[] args) {
		Scanner t=new Scanner(System.in);
		int a=t.nextInt(), cont = 0;
		for(int i=1;i<=a;i++) {
			if(i<=9 && i>=1 || i>=100 && i<1000 || i>=10000 && i<100000 || i>= 1000000 && i<=10000000) {
			cont += 1;
			}
		}
		
		System.out.println(cont);
	}
	}
