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: corporate 
Words: corporation, firm, synergy, tough, concerted
Example Output: tough

Example Input: Category: physical property 
Words: brittleness, large, fat, area, calcium
Example Output: calcium

Example Input: Category: police punishment 
Words: jail, attractive, wispy, prime, fine
Example Output:
attractive