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 boolean func(int n) {
			
			int count = 0;
			while(n != 0) {
				
				n = n/10;
				count++;
			
			}
			
			if(count % 2 == 1){
				
				return true;
				
			} else {
				
				return false;
				
			}
			
		}
		
		
		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(func(i)){
				
					count++;
				
				}
			
			}
			
			System.out.println(count);
			
		}
}