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: type of rigidity
Words: solid, leverage, hard, unbending, firm
Example Output: leverage

Example Input: Category: physical property
Words: obese, heavy, area, chunky, fat
Example Output: heavy

Example Input: Category: elements
Words: fire, burn, ice, air, hire
Example Output:
hire