(:trajectory

(:state (clear b1) (clear b3) (clear b4) (handempty) (on b1 b2) (ontable b2) (ontable b3) (ontable b4))

(:action (unstack b1 b2))

(:state (clear b2) (clear b3) (clear b4) (holding b1) (ontable b2) (ontable b3) (ontable b4))

(:action (stack b1 b2))

(:state (clear b1) (clear b3) (clear b4) (handempty) (on b1 b2) (ontable b2) (ontable b3) (ontable b4))

(:action (pick_up b3))

(:state (clear b1) (clear b4) (holding b3) (on b1 b2) (ontable b2) (ontable b4))

(:action (stack b3 b4))

(:state (clear b1) (clear b3) (handempty) (on b1 b2) (on b3 b4) (ontable b2) (ontable b4))

)