func main()
	var h: int :: cui@inputInt()
	var w: int :: cui@inputInt()
	var s: [][]char :: #[h][]char
	for i(0, h - 1)
		do s[i] :: cui@input()
	end for
	var cnt: int :: 0
	for y(0, h - 1)
		for x(0, w - 1)
			if(s[y][x] = '#')
				do cnt :+ 1
			end if
		end for
	end for
	var ans: bool :: false
	if(cnt <> 0)
		for dy(0, h - 1)
			for dx(0, w - 1)
				if(dy + dx = 0)
					skip dx
				end if
				var ss: [][]char :: ##s
				for y(0, h - 1)
					for x(0, w - 1)
						if(ss[y][x] = '#')
							if(y + dy >= h | x + dx >= w | ss[y + dy][x + dx] = '.')
								skip dx
							end if
							do ss[y + dy][x + dx] :: '.'
						end if
					end for
				end for
				do ans :: true
				break dy
			end for
		end for
	end if
	do cui@print(ans ?("YES\n", "NO\n"))
end func