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 Python (3.4.3) (judge verdict: Wrong Answer)

# -*- coding: utf-8 -*-

def main():
    n = int(input())

    if(n < 10):
        print(n)
    elif(10 <= n < 100):
        print(9)
    elif(100 <= n < 1000):
        print(9 + n - 99)
    elif(1000 <= n < 10000):
        print(999 - 100 + 9)
    elif(10000 <= n < 1000000):
        print(9 - 99 + 999 - 9999 + n)
    else:
        print(9 - 99 + 999 - 9999 + 99999)


if __name__ == "__main__":
    main()