Parent State ID: 20
State Depth: 8
Action Taken: unstack(c, b)
Action Reasoning: To achieve the goal state, we need to place block 'a' on block 'b'. Currently, block 'b' is not clear because block 'c' is on top of it. Therefore, the next best action is to unstack block 'c' from block 'b' to clear block 'b'.
State Description: Block 'a' is held in the hand. Block 'c' is held in the hand after being unstacked from block 'b'. Block 'b' is on the table and is now clear. Block 'd' is on top of block 'c' and is clear. The hand is holding block 'c'.
Action Path: ['unstack(d, a)', 'put-down(d)', 'unstack(a, c)', 'put-down(a)', 'pick-up(d)', 'stack(d, c)', 'pick-up(a)', 'unstack(c, b)']

INACTIVE REASON: deactivated because diagram generation failed or invalid action chosen: Preconditions for unstack(c, b) are not met; 'c' is not clear, and the hand is not empty.
