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{
	static int mod=1000000007;

	public static void main(String[] $){
		System.err.println();
		Scanner s=new Scanner(System.in);
		int n=s.nextInt();
		if(n<=99) {
			System.out.println(Math.min(9,n));
		}else if(n<=9999) {
			System.out.println(Math.min(909,n-99+9));
		}else{
			System.out.println(Math.min(90909,n-9999+909));
		}
	}
}
