m,n=gets.split.map &:to_i
a=(1..m).map{gets}<<""
c=0
m.times{|p|n.times{|q|next if a[p][q]!=?.
x=p
y=q
u=1
v=0
f=0
400.times{if a[z=x+v][w=y-u]==?.
a[x=z][y=w]=?#
u,v=v,-u
f+=1
elsif a[z=x+u][w=y+v]==?.
a[x=z][y=w]=?#
elsif a[z=x-v][w=y+u]==?.
a[x=z][y=w]=?#
u,v=-v,u
end}
c+=x==p&&y==q&&f<2?1:2}}
puts c==1?:YES: :NO