==> real-life/icecubes.p <== You have an old-fashioned refrigerator with a small freezer compartment which could hold seven ice cube trays stacked vertically, but there are no shelves to separate the trays. You have an unlimited supply of trays, each of which can make a dozen cubes, but if you stand one on top of another before it's frozen, it will nest part way into it and you won't get full cubes from the bottom tray. So, what is the fastest way to make ice cubes?