import sequtils, strutils, sugar

var h, w: int
(h, w) = stdin.readLine.split.map parseInt
let ss = (0 ..< h).mapIt stdin.readLine

proc fn(s: string): seq[int] =
  collect newSeq:
    for i, c in s:
      if c == '#': i

let
  ss2 = ss.map fn
  idxs = collect newSeq:
    for i, xs in ss2:
      for x in xs: (i, x)
  length = idxs.len

proc sub(list: var seq[int], val: int): void =
  var idx = 0
  for i, v in list:
    if val == v:
      idx = i
  list.del idx

proc fn2(dist: (int, int)): bool =
  var
    xs = ss2
    cnt = 0

  for (i, j) in idxs:
    if j notin xs[i]:
      continue

    let
      i2 = i.succ dist[0]
      j2 = j.succ dist[1]
    if i2 < 0 or i2 >= h or j2 < 0 or j2 >= w:
      continue

    if j2 notin xs[i2]:
      return false

    sub(xs[i], j)
    sub(xs[i.succ dist[0]], j.succ dist[1])
    inc cnt

    if cnt == length div 2:
      return true

if length == 0 or length mod 2 == 1:
  echo "NO"
else:
  var b: bool
  let list = idxs[1 ..< length]
  for (i, j) in list:
    let dist = (i.pred idxs[0][0],j.pred idxs[0][1])
    b = fn2 dist
    if b:
      break

  if b:
    echo "YES"
  else:
    echo "NO"