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No
 No
 No
 Yes
 Yes
 No
 Yes
 Yes
 Yes
 No
 Yes
 No
 No
 Yes
 No
 Yes
 No
 No
 Yes
 No
 No
 No

bl,wt='# .'.split()

def vhs(v,h,w):
	"""vertical horizontal sums"""
	vr,hr=[],[]
	for c in range(h):
		vr.append(v[c].count(bl))
	for d in range(w):
		ts=''.join([v[c][d] for c in range(h)])
		hr.append(ts.count(bl))
	return vr,hr

def gcr(v,h,w):
	"""get cross"""
	dh=dict()
	vr,hr=vhs(v,h,w)
	for c in range(h):
		for d in range(w):
			if v[c][d]==bl and vr[c]>1 and hr[d]>1:
				dh.setdefault(c,[]).append(d)
	return dh

def ic(v,h,w):
	"""is correct"""
	dh=gcr(v,h,w)
	ldh=len(dh)
	if ldh==0:
		return 1
	elif ldh==1:
		return 0
	#print(dh)
	sv=dh[min(dh.keys())]
	if len(sv)==1:
		return 0
	for v in dh.values():
		if sv!=v:
			return 0
	return 1

h,w=[int(c) for c in input().split()]
v=[]
for c in range(h):
	v.append(input())
s='YES' if ic(v,h,w) else 'NO'
print(s)