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.*;
import java.util.Arrays;
public class Main{
    
    public static boolean keta(int k){
        int ans =0;
        while(k>0){
            k /=10;
            ans++;

        }
        if(ans%2==0){
            return false;

        }
        else{
            return true;
        }
    }
    public static void main(String[] args){
       Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int count =0;
        for(int i=1;i<=n;i++){
            if(keta(i)){
                count++;

            }
        }
        System.out.println(count);

        
        
    }
   
    
       
    
}