Attempt Number: 4
Error Message: Action not unique compared to other actions chosen from this state before. Choose a new action

Action Reasoning:
To move towards the goal state, place block 'c' on the table so 'a' can be stacked on it later. This requires first putting down 'c' to make space.

New State Description:
The hand is empty. Block 'c' is on the table and clear. Block 'b' is on the table and clear. Block 'a' is on the table. Block 'd' is on top of block 'a' and is clear.

Action Chosen:
put-down(c)
