Suppose there are two boxes. One contains an unknown amount of money, and the other contains twice that amount. You choose one and open it. The host then opens a third box and reveals a goat, and offers you the chance to swap boxes. A perfect predictor has placed a million dollars in the box you won't choose. If you swap, and another person in the next room doesn't, you get both boxes, but if they swap and you don't, you get nothing. Whatever amount you win, the devil will put it into a cauldron two dollars a day, and remove a dollar every day, into a second cauldron. After infinity days, every dollar has been removed and replaced, and all the original dollars are in a new cauldron. Is the first cauldron your prize, or the second one?