Every state that means "a full toy has just been scanned" is a valid accepting state. In fact you don't need separate states for each toy, you only need self-lo

Every state that means "a full toy has just been scanned" is a valid accepting state. In fact you don't need separate states for each toy, you only need self-loop of appropriate length. (Also, this is an NFA, not a DFA) The language of valid parentheses up to size 2^5 is obviously regular, it's even finite.