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 void main(String[] args) {
        Scanner in = new Scanner(System.in);
        String str = in.nextLine();
        int a = 9;
        int b = 900;
        int c = 90000;
        if (str.length() == 2) {
            System.out.println(a);
        } else if (str.length() == 4) {
            System.out.println(a + b);
        } else if (str.length() == 6) {
            System.out.println(a + b + c);
        } else if (str.length() == 1) {
            System.out.println(str);
        } else if (str.length() == 3) {
            int d = Integer.parseInt(str) - 99;
            System.out.println(a + d);
        } else if (str.length() == 5) {
            int d = Integer.parseInt(str) - 9999;
            System.out.println(a + b + d);
        }
    }
}