Lemma expf_B0_CS_2:forall (m:fmap)(x z t:dart), inv_hmap m -> succ m zero x -> let x0 := cA m zero x in let xb0 := bottom m zero x in ~expf m x0 xb0 -> (expf m xb0 z /\ expf m x0 t \/ expf m xb0 t /\ expf m x0 z \/ expf m z t) -> expf (B m zero x) z t.