Current State ID: 0
Current State Description: In the initial state, block c is on the table. Block b is stacked on top of block c. Block d is on top of block b, and block a is on top of block d. The hand is empty, and block a is clear, meaning there is no block on top of it.

Child State ID: 1
Action Taken: unstack(block_a, block_d)
State Description: Block 'a' is held by the hand and is no longer on block 'd'. Block 'd' is now clear. Block 'b' is supporting block 'd'. Block 'c' is supporting block 'b'. The table supports block 'c'. The hand is not empty as it holds block 'a'.

