Most Hrunkla lived in giant, 12-story apartment houses, and their homes were large square rooms bounded on four sides by corridors. Each room had a single door which opened halfway along a corridor. On even-numbered floors, the doors opened onto the east corridor; on odd-numbered floors, the doors opened onto the north corridor. At each intersection of corridors, there was something like an elevator which could be ridden up or down. Half of the corridors had moving belts on the floor, and no self-respecting Hrunkla would walk if he could ride one of these belts. The belts were so arranged that those on floors 1, 5, and 9 ran to the east; those on floors 2, 6, and 10 ran to the south; those on floors 3, 7, and 11 ran to the west; and those on floors 4, 8, and 12 ran to the north.
Describe how a Hrunkla who lived on floor 10 could use these moving belts and elevators to visit a friend who lived in the room directly below his.