Torturing people for fun

Most of the usual thought experiments that justify expected utilitarialism trade off fun for fun, or suffering for suffering. Here’s a situation which mixes the two. You are offered to press a button that will select a random person (not you) and torture them for a month. In return the machine will make N people who are not suffering right now have X fun each. The fun will be of the positive variety, not saving any creatures from pain.

1) How large would X and N have to be for you to accept the offer?

2) If you say X or N must be very large, does this prove that you measure torture and fun using in effect different scales, and therefore are a deontologist rather than a utilitarian?