Starting state: there are 5 stacks: - Stack 1: blue block (alone) - Stack 2: green block (alone) - Stack 3: purple block (alone) - Stack 4: orange block (alone) - Stack 5: yellow block (alone) Ending state: there are 2 stacks: - Stack 1: green block, purple block, from bottom to top - Stack 2: orange block, blue block, yellow block, from bottom to top