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 {
	Scanner sc = new Scanner(System.in);
	final int MOD = 1000000007;
	final int MAX = Integer.MAX_VALUE;
	final long LMAX = Long.MAX_VALUE;
 
	void doIt() {
		int n = sc.nextInt();
		if(n >= 1000 && n <= 9999) {
			n = 909;
		}
		else if(n >= 10 && n <= 99) {
			n = 9;
		}
		else {
			if(n >= 100000) {
				n -= 9091;
			}
			else if(n >= 1000) {
				n -= 9090;
			}
			else if(n >= 10) {
				n-=90;
			}
			
		}
		System.out.println(n);
	}
 
	public static void main(String[] args) {
		new Main().doIt();
	}
}