There is a very popular theory saying that it's 3. I think it was the counting theory...
It can be any number. It depends on what you're doing... Counting? Multiplying? Subtracting? Division?...
We don't know yet. There has to be a movie made of it before the author can start working on the next book. To be a movie, more people have to buy the book. But the next book's going to be about Pru!...