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.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

class Main{

    public static int digits(int x)
    {
        int n =0;

        while(x>0)
        {
            x=x/10;
            n++;
        }

        return n;
    }

    public static void main(String[] args)  throws IOException {
        // write your code here

        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        int t = Integer.parseInt(reader.readLine());

        //int dig = digits(t);

        int ct=0;

        for(int i=1;i<=t;i++)
        {
            int dig = digits(i);

            if(dig%2!=0)
            {
                ct++;
            }
        }

        System.out.println(ct);

    }
}