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 sys

def solve(n):
  count = 0
  for i in xrange(n):
    i += 1
    if 10 <= i < 100:
      continue
    if 1000 <= i < 10000:
      continue
    if 100000 <= i:
      continue

    count += 1

  return count

if __name__ == '__main__':

  n = int(sys.stdin.readline().strip())
  print solve(n)