Current State ID: 2
Current State Description: The hand is empty. Block 'b' is on the table and clear. Block 'a' is on the table. Block 'd' is on top of block 'a'. Block 'c' is on top of block 'd' and is clear. Block 'b' is not on any other block.

Child State ID: 4
Action Taken: unstack(c, d)
State Description: The hand is holding block 'c'. 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. Block 'c' is no longer on block 'd' and is held by the hand.

