Current State ID: 18
Current State Description: Block 'a' is on the table and clear. Block 'c' is clear and on top of block 'b'. Block 'b' is on the table. Block 'd' is on the table and clear. The hand is empty.

Child State ID: 21
Action Taken: unstack(c, b)
State Description: Block 'a' is on the table and clear. Block 'c' is held in the hand. Block 'b' is on the table and clear. Block 'd' is on the table and clear. The hand is holding block 'c'.

