GAIM intern Emily takes you step by step through 2019 GAIM counting problem "Radium: Poison".
Problem text:
Potion A is poison. Potion B is water. Potion C is lemonade. Potion D is antidote. There is an unlimited supply of each potion.
Shirley takes three sips in a row, not necessarily of different potions.
If she takes at least one sip of the poison, she will be poisoned unless she also drinks the antidote. If Shirley drinks a sip of antidote at any time, it will protect her from even a double dose of poison. How many different drink orders result in her not being poisoned at the end of her three sips?
(For example, antidote, poison, poison and poison, poison, antidote are both safe drink orders.)