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