Given a sentence, fill out the missing word with a 'no' or a number (between zero and ten). You should write the numbers with english alphabet, like: four instead of 4.

Example Input: Prions are protein molecules which have ____ metastable states.
Example Output: two

Example Input: Ozone is formed of ____ atoms of oxygen.
Example Output: three

Example Input: Economists divide resources into ____ basic categories - land, labor, capital and management.
Example Output:
four