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);
      
      //入力
      int N = sc.nextInt();
      int count = 0;
      
      //桁数を取得する
      for(int i=1; i<=N; i++){
        int V = String.valueOf(i).length();
        
       //桁数が奇数のときカウント
        if(V%2!=0){
        	count++;
        }
      }
      //出力
      System.out.println(count);
    }
}