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: animal 
Words: bus, leap, spider, run, fly
Example Output: bus

Example Input: Category: construction 
Words: hoist, tackle, digger, excavator, crane
Example Output: tackle

Example Input: Category: animal 
Words: cow, shark, raft, fish, goat
Example Output:
raft