A necromancer is exploring a dungeon with his trusty skeleton bodyguard, a charmed goblin, and a big bag of loot. He comes to a river of lava cutting across a chamber, preventing further progress to those without magical assistance.
The necromancer casts fly on himself, and then floating disk. But he has a problem. The floating disk is only big enough to carry one of the three -- skeleton, goblin, treasure -- at a time.
If he leaves the skeleton and goblin alone, the skeleton will kill the goblin. If he leaves the goblin and treasure alone, the goblin will make off with it.
So what's the optimal way for the necromancer to get his henchmen and loot across the lava?