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: water vapor condensing in clouds causes rain.
Example Output: clouds vapor.

Example Input: Fact: Evolution occurs by a process called natural selection.
Example Output: evolution changing.

Example Input: Fact: Grasses supply most of the food consumed by people worldwide.
Example Output:
grasses are plants.