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

Example Input: squashed, cabin, flat, smooth, round
Example Output: smooth

Example Input: fair, mild, loyal, alright, trustworthy
Example Output: mild

Example Input: firm, sustainability, ceo, tough, corporation
Example Output:
tough