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: secretary duty 
Words: support, fax, file, download, errands
Example Output: download

Example Input: Category: elements 
Words: pay, cool, combustion, air, fire
Example Output: pay

Example Input: Category: bird 
Words: crane, tackle, parrot, mallet, neck
Example Output:
tackle