class Integer
  def invalid_id?
    string = to_s
    return false if string.length.odd?
    
    string[..((string.length / 2) - 1)] == string[(string.length / 2)..]
  end

  def silly_invalid_id?
    string = to_s
    for pattern_length in 1.upto(string.length - 1)
      next if string.length % pattern_length != 0

      pattern = string[0..(pattern_length - 1)]
      rest = string[pattern_length..]
      return true if rest.gsub(pattern, "").empty?
    end

    false
  end
end

class IdRange
  attr_reader :range
  def initialize(range)
    @range = range
  end

  def self.for(chunk)
    low, high = chunk.split("-").map(&:to_i)
    new low..high
  end

  def invalid_ids
    range.select(&:invalid_id?)
  end

  def silly_invalid_ids
    range.select(&:silly_invalid_id?)
  end
end