Implement:
to_words(n) for integers with absolute value below 10¹²: 0 → "zero", 123 → "one hundred twenty-three", 1005 → "one thousand five", -42 → "minus forty-two". Use the scale words thousand, million and billion, hyphenate 21–99, and don't use "and".from_words(text): the inverse, for any string to_words can produce