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.

Ex Input:
Category: type of rigidity 
Words: rigged, firm, unyielding, streamline, taut

Ex Output:
streamline


Ex Input:
Category: bird 
Words: ostrich, digger, sandpiper, crane, goose

Ex Output:
digger


Ex Input:
Category: bird 
Words: hummingbird, tackle, crane, hoist, tackle

Ex Output:

tackle