Given a category and a set of five words, find the word from the set that does not belong (i.e. is the least relevant) with the other words in the category. Words are separated by commas.

Example Input: Category: animal 
Words: bus, leap, spider, run, fly
Example Output: bus

Example Input: Category: animal 
Words: fish, bat, sea turtle, trap, goat
Example Output: trap

Example Input: Category: baby animals 
Words: expression, fawn, hatchling, calf, deer
Example Output:
expression