Parent State ID: 18
State Depth: 9
Action Taken: stack(a, c)
Action Reasoning: To achieve the goal state, block 'a' should be on block 'c', and block 'd' should be on block 'a'. The first step is to stack block 'a' on block 'c', as both are clear and on the table.
State Description: The hand is empty. Block 'a' is now on top of block 'c' and is clear. Block 'b' is clear and remains on the table. Block 'c' is supporting block 'a' and is on the table. Block 'd' is clear and remains on the table.
Action Path: ['unstack(b, c)', 'put-down(b)', 'unstack(c, d)', 'put-down(c)', 'unstack(d, a)', 'put-down(d)', 'pick-up(c)', 'put-down(c)', 'stack(a, c)']

INACTIVE REASON: deactivated because diagram generation failed or invalid action chosen: The hand is not holding block 'a', violating the precondition for stacking.
