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.

Input: Consider Input: Fact: Immunodeficiency occurs when the immune system is not working properly.

Output: immune system keeps people healthy.


Input: Consider Input: Fact: Sweating reduces body heat.

Output: "body heat" reduces sweating.


Input: Consider Input: Fact: propulsion is used for flying by a spacecraft.


Output: propulsion spacecraft.