#!/usr/bin/ruby
require 'rubygems'
require 'facets'


class Numbers
  
  # Вся оптимизация заключается в замене этой строчки на Denumerable.
  is Enumerable
  
  def initialize(source_io)
    @io = source_io
  end
  
  def each
    yield @io.gets.to_f until @io.eof?
  end
  
end


def main(input, output)
  Numbers.new(input).collect { |x| if x > 0 then x * 2; else x; end }.each { |x| output.puts x }
end


# --- Runner ---

if %W{-h --help}.include? ARGV[0]
  puts <<HELP
School task v1.0.

Usage: school_task [file]

File contains numbers delimited with new lines. If file is omitted, standard
input is used.

Result is in the same format as input and is passed to standard output.

Errors in input are not handled.
HELP
  exit
end


if ARGV[0] then File.open(ARGV[0]) { |input| main(input, STDOUT) }
else main(STDIN, STDOUT); end