Current State ID: 0
Current State Description: There are four blocks: a, b, c, and d. The hand is empty. Block a is on the table. Block b is on top of block a. Block c is on top of block b. Block d is on the table. Block c is clear, meaning there is no block on top of it. Block d is clear, meaning there is no block on top of it.

Child State ID: 1
Action Taken: unstack(c, b)
State Description: The hand is holding block c. Block a is on the table. Block b is on top of block a and is now clear. Block c is no longer on block b and is not clear. Block d is on the table and clear.

