Diagram in problem sovling with mathematics?

10 goes east out his door and is belted to elevator at the south east corner of his home. He goes to the 11th floor, where he is belted to the elevator that runs at the south west corner of his house. He goes to the 12th floor and is belted to the elevator at the north west corner. He then goes down to the 9th floor and is immediately belted to the door on the north side of his friends house. The only walking involves getting on and off belts and elevators