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