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 activity 
Words: tumble, summer, fall, bend, lift
Example Output: summer

Example Input: Category: animal 
Words: walk, flap, fish, fly, bats
Example Output: flap

Example Input: Category: mode of transportation 
Words: flap, cockroach, fly, jog, soar
Example Output:
cockroach