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: physical property 
Words: obese, fat, vitamin c, heavy, thin
Example Output: vitamin c

Example Input: Category: secretary duty 
Words: answer calls, image, organize, file, correspondence
Example Output: image

Example Input: Category: bird 
Words: flamingo, hoist, derrick, crane, hoist
Example Output:
hoist