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;

/**
 * B - Uneven Numbers
 * 整数 N が与えられます。
 * N 以下の正の整数のうち、(先頭に 0 をつけずに十進法で表記したときの) 桁数が奇数であるようなものの個数を求めてください。
 */
public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner( System.in );
        // 確認する数値
        int n = sc.nextInt();
        int result = 0;

        for( int i = 1; i <= n; i++ ) {
            if( String.valueOf( i ).length() % 2 != 0 ) {
                result++;
            }
        }

        System.out.println( result );

        sc.close();
    }
}