Current State ID: 0
Current State Description: There are four blocks: a, b, c, and d. Block b is on the table. Block c is on top of block b. Block a is on top of block c. Block d is on top of block a. The hand is empty, and block d is clear.

Child State ID: 1
Action Taken: unstack(d, a)
State Description: Block d is in the hand, block a is clear and on top of block c, block c is on top of block b, and block b is on the table. The hand is holding block d.

