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: nutritional value 
Words: fat, protein, vitamin c, fiber, area
Example Output: area

Example Input: Category: secretary duty 
Words: support, type, file, software, answer
Example Output: software

Example Input: Category: type of rigidity 
Words: rigged, unyielding, firm, resistant, united
Example Output:
united