building up and some kind of popping the stack by pushing through the stack the sequence of bits that it code a sequence of symbols with this mixture model or bits back coding so we really see is the bits that we're getting back or not visitor sitting off to the side necessarily they're bits that came onto our stack from encoding the previous symbol that we encoded this way and you might wonder well if we took it off here but put other things on have we lost the ability to get those bits back no that's the whole idea in the decoding as we saw