that 's its first sign of trouble . 
(ROOT (S (NP (DT that)) (VP (VBZ 's) (NP (NP (PRP$ its) (JJ first) (NN sign)) (PP (IN of) (NP (NN trouble))))) (. .)))
(ROOT (S (NP (DT )) (VP (VBZ ) (NP (NP (PRP$ ) (JJ ) (NN )) (PP (IN ) (NP (NN ))))) (. )))