L Staircase (6 rooms, all grade 3)L2 Staircase (7 rooms, grades 2-3)M Staircase (16 rooms, grades 1-3)M2 Staircase (12 rooms, grades 2-3)U Staircase (17 rooms, grades 1-3)V Staircase (12 rooms, grades 3-4)