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.*;

class Main {
  public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);
      int N = sc.nextInt();
      int Ans = 0;
      if(N<10) {
    	  Ans = N;
      }
      else if(N<100) {
    	  Ans = 9;
      }
      else if(N<1000) {
    	  Ans = N -100 +10;
      }
      else if(N<10000) {
    	  Ans = 900 + 9;
      }
      else if(N<100000) {
    	  Ans = N-10000 + 910;
      }else {
    	  Ans = 90909;
      }
      System.out.println(Ans);
  }
}