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();
		sc.close();
		
		int count = 0;
		for(int i=1;i<=N;i++) {
			
			//111 -> 11 -> 1 -> 0
			int cnt = 0;
			
			int tmp = i;
			
			while(tmp != 0) {
				tmp/=10; // i = i / 10 ;  i = i + 3 -> i+=3; i = i+1 -> i++
				cnt ++;
			}
			
			if(cnt % 2 == 1) count ++;
			
		}
		System.out.println(count);
	}
	
}