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 sc = new Scanner(System.in);

		int N =sc.nextInt();

		switch(String.valueOf(N).length()) {
		case 1:
			System.out.println(N);
			break;
		case 2:
			System.out.println(9);
			break;
		case 3:
			System.out.println(9 + (N - 100) + 1);
			break;
		case 4:
			System.out.println(909);
			break;
		case 5:
			System.out.println(909 + (N - 10000) + 1);
			break;
		default:
			System.out.println(90909);
			break;
		}
	}

}