them would back leave gravel remains in the stones .
(ROOT_0 (S_0 (ATS_3 (NP_1 (PRP_0 them)) (VP_4 (ATVP_1 (MD_0 would) (ADVP_0 (RB_0 back))) (VP_5 (ATVP_4 (VB_0 leave) (NP_2 (JJ_1 gravel) (NNS_1 remains))) (PP_2 (IN_0 in) (NP_6 (DT_0 the) (NNS_1 stones)))))) (DOT_0 .)))