#!/usr/bin/ruby
# coding: utf-8
#【薙刀式】1文字置きの頻度転がってないかなあ
# http://oookaworks.seesaa.net/article/464057945.html

prev_letter = String.new
$stdin.read.each_char do |letter|
  prev_letter << letter
  if not prev_letter[-3].nil?
    if prev_letter[-3] == "\n"
      print "[LF]"
    else
      print prev_letter[-3]
    end
    if letter == "\n"
      puts "[LF]"
    else
      puts letter
    end
  end
end