stems = ARGF.read
            .split
            .each_cons(2)
            .group_by { |word_pair| word_pair[0] }

def next_word ary
  ary[rand(ary.length).to_i][1]
end

e = Enumerator.new do |e|
  word = stems.first.first
  while word
    e << word
    word = next_word(stems[word] || stems.first)
  end
end