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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;

public class Main {
    public static int N = 0;
    public static String output = "";

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        N = sc.nextInt();
        int length = String.valueOf( N ).length();
        if (length == 6) {
            output = Integer.toString(9 + 900 + 90000);
        }
        else if (length == 5) {
            output = Integer.toString(9 + 900 + (N - 9999));
        }
        else if (length == 4) {
            output = Integer.toString(9 + 900);
        }
        else if (length == 3) {
            output = Integer.toString(9 + (N - 99));
        }
        else if (length == 2) {
            output = Integer.toString(9);
        }
        else if (length == 1) {
            output = Integer.toString(N);
        }

        System.out.println(output);
    }
}