Given reviews from Amazon, classify those review based on their content into two classes: Negative or Positive.

I bought this air mattress two months ago. I used a couple of days and it worked fine. Now a friend is planning to visit so I decided to use it again but something went wrong, instead of a flat surface, there is a huge bump in the middle that would make sleeping on it uncomfortable if not impossible.Since this is a product you will use only a couple of days before putting it away until you need it again, the amazon returning period will be over by the time you actually try it and find something wrong with it. And the company that makes this mattress says "this product does not have any warranty or service program". I hope I can put this in the recyclables bin!I wish I would've spend a little bit money on a real mattress that won't fail after a while.
Negative