it should have stayed there . 
(ROOT (S (NP (PRP it)) (VP (MD should) (VP (VB have) (VP (VBN stayed) (ADVP (RB there))))) (. .)))
(ROOT (S (NP (PRP )) (VP (MD ) (VP (VB ) (VP (VBN ) (ADVP (RB ))))) (. )))