, comedian runs out of steam after a half hour . 
(ROOT (S (, ,) (NP (NN comedian)) (VP (VBZ runs) (PP (IN out) (PP (IN of) (NP (NN steam)))) (PP (IN after) (NP (DT a) (JJ half) (NN hour)))) (. .)))
(ROOT (S (, ) (NP (NN )) (VP (VBZ ) (PP (IN ) (PP (IN ) (NP (NN )))) (PP (IN ) (NP (DT ) (JJ ) (NN )))) (. )))