Parent State ID: 16
State Depth: 5
Action Taken: pick-up(a)
Action Reasoning: To achieve the goal state, we need to stack block 'a' on block 'd'. Since both blocks are clear and the hand is empty, the next best action is to pick up block 'a'.
State Description: Block a is held in the hand. Blocks b, c, and d remain clear and on the table. The hand is no longer empty.
Action Path: ['unstack(c, b)', 'put-down(c)', 'unstack(d, a)', 'put-down(d)', 'pick-up(a)']
