Slothouber–Graatsma puzzle

The Slothouber–Graatsma puzzle is a packing problem that calls for packing six 1 × 2 × 2 blocks and three 1 × 1 × 1 blocks into a 3 × 3 × 3 box (all shapes being right angled). The solution to this puzzle is unique (up to mirror reflections and rotations).