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.lang.*;
import java.util.*;
 
public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int kari = n+1;
        int keta = 1;
        while((int)(kari/10)!=0){
            keta++;
            kari = (int)(kari/10);
        }
        if(keta == 1){
            System.out.println(n);
        }else if(keta == 2){
            System.out.println(9);
        }else if(keta == 3){
            System.out.println((10+n-100));
        }else if(keta == 4){
            System.out.println(909);
        }else if(keta == 5){
            System.out.println((910+n-10000));
        }else{
            System.out.println(90909);
        }
        sc.close();
    }
}