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 {

    void solve() {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int count = 0;
        for (int i = 1; i <= N; i++) {
            if ((1 <= i && i <= 9) || (100 <= i && i <= 999) || (10000 <= i && i <= 99999)) {
                count++;
            }
        }
        System.out.print(count);
    }

    // Main
    public static void main(String[] args) {
        new Main().solve();
    }
}