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 cnt = 0;	

  	for (int i=N;i>0;i--){
      if(((0<i)&&(i<10))
         ||((99<i)&&(i<1000))
         ||((9999<i)&&(i<100000))){
         cnt++;
      }
    }
 
  	System.out.println(cnt);
  
	}
}