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)

N = int(input())
 
result = 0
if len(str(N)) % 2 == 0:
    loop = ((len(str(N)) - 1) -1) //2 + 1
    #print(loop)
    for i in range(loop):
        result += 9 * pow(10,2*i)
else:
    for i in range(len(str(N)) - 2):
        result += 9 * pow(10,i)
    result += N - pow(10,len(str(N)) - 1) + 1
 
print(result)