While designing Push Down Automata consider my inputs are {a,b} Now can I push multiple a's or multiple b's while scanning them...and then while popping can I pop multiple number of a's or multiple number of b's... OR is it the case that I can push/pop only one element at a time i.e. pushing single 'a' or single 'b' and also while popping out only single 'a' or single 'b'?