Alternate Plot

Use the same premise. Assume that while there are 333 levels only fewer than say 250 are actually used. If you get to the bottom level (333) then you can simply walk out of the prison free. The thing is no one knows about this get out of jail free exit. So everyone behaves similar to as in this film.

New protagonist somehow learns this secret (maybe from another dying inmate). Then the journey down past all the starving maniacs begins. Perhaps taking to long the first time and being sent back up at the end of the month.