Divide angels into a and demons into B.
aaaabbb
AB, get on the boat. One, come back.
AABB B
BB get on the boat and b come back.
AAAB BB
AA ABoard, ab back.
AABB company
AA, come back on the boat.
BBB AAA
BB get on the boat and b come back.
BB get on board
All right! it's over