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.

Examples

Input

11


Output

9


Input

136


Output

46


Input

100000


Output

90909
import math
inp = raw_input("")
n = int(inp)
base = int(math.log10(n))
total = 0
for i in range(0, base, 2):
  total += 9 * (10 ** i)
if base % 2 == 0:
  total += n - (10 ** base) + 1
print total
