h,w=map(int,input().split())
s=[input() for i in range(h)];ans="NO"
for i in range(0,h+1):
	for j in range(-w,w+1):
		if not i and not j:
			continue
		b=1
		c=[[0]*w for i in range(h)]
		for l in range(h):
			for k in range(w):
				if c[l][k] or s[l][k]==".":
					continue
				u,v=l+i,j+k
				if u<0 or u>=h or v<0 or  v>=w or s[u][v]==".":
					b=0;break
				c[u][v]=1
			if not b:
				break
		if b:
			ans="YES"
print(ans)