Parent State ID: 30
State Depth: 9
Action Taken: pick-up(a)
Action Reasoning: To achieve the goal state, we need to stack block 'a' on block 'b'. First, we must pick up block 'a' from the table.
State Description: Block 'a' is held in the hand. Block 'b' is on the table and clear. Blocks 'c' and 'd' are on the table and clear. The hand is holding block 'a'. The diagram would show block 'a' marked as held, with the hand no longer empty.
Action Path: ['unstack(d, a)', 'put-down(d)', 'unstack(a, c)', 'put-down(a)', 'pick-up(d)', 'put-down(d)', 'unstack(c, b)', 'put-down(c)', 'pick-up(a)']
