def count_words(string)
  str = string.downcase
  str = str.gsub(/\b/, '-')
  words = str.scan(/-([a-z]+)-/)
  count = Hash.new(0)
  words.each do |word|
    count[word] += 1
    puts word
  end
  return count
end
c = count_words("This is a sentence")
puts c, c["is"]