We should have left then.
1	We	we	PRON	PRP	Case=Nom|Number=Plur|Person=1|PronType=Prs	4	nsubj	4:nsubj	_
2	should	should	AUX	MD	VerbForm=Fin	4	aux	4:aux	_
3	have	have	AUX	VB	VerbForm=Inf	4	aux	4:aux	_
4	left	leave	VERB	VBN	Tense=Past|VerbForm=Part	0	root	0:root	_
5	then	then	ADV	RB	PronType=Dem	4	advmod	4:advmod	SpaceAfter=No
6	.	.	PUNCT	.	_	4	punct	4:punct	_
