Problem:
Score : 200 points

Problem Statement

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.

Sample Input 1

11

Sample Output 1

9

Among the positive integers less than or equal to 11, nine integers have an odd number of digits: 1, 2, \ldots, 9.

Sample Input 2

136

Sample Output 2

46

In addition to 1, 2, \ldots, 9, another 37 integers also have an odd number of digits: 100, 101, \ldots, 136.

Sample Input 3

100000

Sample Output 3

90909

Solution in Java (OpenJDK 11.0.6) (judge verdict: Accepted)


public class Main {

    public static void main(String[] args) {

        java.util.Scanner sc = new java.util.Scanner(System.in);

        int n = sc.nextInt();

        int count = 0;

        for (int i = 1; i <= n; i++) {
            if (("" + i).length() % 2 == 1) {
                count++;
            }
        }

        System.out.println(count);

    }

}