def f(m,dx,dy,h,w)
	i=0
	arr=Array.new(h*2+3).map{Array.new(w*2+3,0)}
	c=0
	m.each{|e|
		j=0
		e.chars{|e2|
			if e2=="#"
				arr[i][j]=1
				c+=1
			else
				arr[i][j]=0
			end
			j+=1
		}
		i+=1
	}
	
	h.times{|y|
		w.times{|x|
			y1=y+dy
			x1=x+dx
			if arr[y][x]==1
				arr[y1][x1]-=1
				c-=2
			end
			return false if arr[y1][x1]<0
		}
	}
	return c==0
end

h,w=gets.split.map{|e| e.to_i}
m=[]
h.times{
	m<<gets.chomp
}



ok=false
h.times{|dy|
	w.times{|dx|
		if dy+dx!=0
			ok=ok||f(m,dx,dy,h,w)
		end
	}
}
if ok==true
	puts "YES"
else
	puts "NO"
end