def f(a)
  answer_xored = 0
  lower_xors = 0

  a.each do |e|
    answer_xored = answer_xored ^ e
  end

  a.each do |e|
    solution_pairing = e ^ answer_xored
    lower_num = [e, solution_pairing].min
    if e == lower_num
      lower_xors = lower_xors ^ e
    end
  end

  return [lower_xors, lower_xors ^ answer_xored]
end