You should be fine with just a passport, unless you're staying longer than six months.
1	You	you	PRON	PRP	Case=Nom|Person=2|PronType=Prs	4	nsubj	4:nsubj	_
2	should	should	AUX	MD	VerbForm=Fin	4	aux	4:aux	_
3	be	be	AUX	VB	VerbForm=Inf	4	cop	4:cop	_
4	fine	fine	ADJ	JJ	Degree=Pos	0	root	0:root	_
5	with	with	ADP	IN	_	8	case	8:case	_
6	just	just	ADV	RB	_	8	advmod	8:advmod	_
7	a	a	DET	DT	Definite=Ind|PronType=Art	8	det	8:det	_
8	passport	passport	NOUN	NN	Number=Sing	4	obl	4:obl:with	SpaceAfter=No
9	,	,	PUNCT	,	_	4	punct	4:punct	_
10	unless	unless	SCONJ	IN	_	13	mark	13:mark	_
11-12	you're	_	_	_	_	_	_	_	_
11	you	you	PRON	PRP	Case=Nom|Person=2|PronType=Prs	13	nsubj	13:nsubj	_
12	're	be	AUX	VBP	Mood=Ind|Number=Sing|Person=2|Tense=Pres|VerbForm=Fin	13	aux	13:aux	_
13	staying	stay	VERB	VBG	Tense=Pres|VerbForm=Part	4	advcl	4:advcl:unless	_
14	longer	long	ADV	RBR	Degree=Cmp	13	advmod	13:advmod	_
15	than	than	ADP	IN	_	17	case	17:case	_
16	six	six	NUM	CD	NumForm=Word|NumType=Card	17	nummod	17:nummod	_
17	months	month	NOUN	NNS	Number=Plur	14	obl	14:obl:than	SpaceAfter=No
18	.	.	PUNCT	.	_	4	punct	4:punct	_
