In this task, you need to write a topic word from the given fact. The topic word must have at least one word overlap with the given fact. The topic word often involves adding a new word from a related concept. In your topic word, use at least one word from the given fact. Topic words with two or more words work best.

Example Input: Fact: the movement of an air mass over Earth 's surface causes local weather changes.
Example Output: air mass front.

Example Input: Fact: Blood type is important for medical reasons.
Example Output: blood type a b o.

Example Input: Fact: Pedigrees are useful tools for studying inheritance patterns.
Example Output:
inheritance animals.