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: Runtime Error)

import java.util.*;

class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		String input = sc.next();
		int len = input.length();
		int num = Integer.parseInt(input);
		int ans = 0;
		switch(len%2){
			case 0:
			for(int i = 0; i < len; i+=2)ans += 9 * Math.pow(10, i);
			break;

			case 1:
			for(int i = 0; i < len-1; i+=2)ans += 9 * Math.pow(10, i);
			ans += Integer.parseInt(input.substring(1))+1;
			break;
		}

		System.out.println(ans);
	}
}