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.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int t = 0,count = 0;
		int b = a;
		while (b>0){
			b = b/10;
			t ++;
		}
		for (int i = 1; i < t; i+=2){
			if (i==1){
				count+=9;
			} else {
				int min=1,max=9,j=i;
				while (j>1){
					min*=10;
					max*=10;
					max+=9;
					j--;
				}
				count+=max-min;
				count++;
			}
		}
		if(t%2==1) {
			int min = 1,j = t;
			while (j>1){
				min*=10;
				j--;
			}
			count+=a-min;
			count++;
		}
		System.out.println(count);
		sc.close();
	}
}