each story is built on a potentially interesting idea 
(ROOT (S (NP (DT each) (NN story)) (VP (VBZ is) (VP (VBN built) (PP (IN on) (NP (DT a) (ADJP (RB potentially) (JJ interesting)) (NN idea)))))))
(ROOT (S (NP (DT ) (NN )) (VP (VBZ ) (VP (VBN ) (PP (IN ) (NP (DT ) (ADJP (RB ) (JJ )) (NN )))))))