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.*;
public class Main{
    public static void main(String[]args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();

        int ans  = 0;

        for(int i = 1; i <= n ; i++){
            if(i >= 10 && i <= 99) continue;
            if(i >= 1000 && i <= 9999) continue;
            if(i == 100000) continue;

            ans++;
        }

        System.out.println(ans);
        return;
    }
}