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 {

		static void solve() {
			Scanner sc = new Scanner(System.in);
			int n = sc.nextInt();
			int res = 0;
			sc.close();
			for(int i = 1;i<=n;i++) {
				String s =String.valueOf(i);
				if(s.length()%2!=0){
					res++;
				}
			}
			System.out.println(res);
		}
	public static void main(String[] args) {
		solve();

	}

}
