while true do
  to_test = files.first
  max_size = 0
  max_common = ""

  files.each do |f|
    if f != to_test
      common = Util::longest_common_substring(to_test, f)
      if common.size > max_size && f.size - common.size >= mindiff
        max_common = common
        max_size = common.size
      end
    end
  end

  print max_common + "\n"

  blocks[max_common] = files.select { |s| s.include? max_common }
  files.select! { |s| !s.include? max_common }
  if files.size == 0
    break
  end
end