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: neat, beautiful, dull, fine, firstrate
Example Output: firstrate

Example Input: happy, substance, shop, tools, content
Example Output: happy

Example Input: opposite of up, kind, down, backward, south
Example Output:
kind