local ior = io.input()
local h, w = ior:read("*n", "*n", "*l")
local t = {}
local str = ""
for i = 1, h do
  str = ior:read()
  for j = 1, w do
    t[j + (i - 1) * w] = str:sub(j, j) == "#" and 1 or 0
  end
end

local function check(hdiff, wdiff)
  local tbl = {unpack(t)}
  local ret = true
  local painted = false
  for i_h = 1, h do for j_w = 1, w do
    local idx = j_w + (i_h - 1) * w
    if(tbl[idx] == 1) then
      painted = true
      if(h < i_h + hdiff or j_w + wdiff < 1 or w < j_w + wdiff) then
        ret = false break
      end
      local dst = idx + w * hdiff + wdiff
      if(tbl[dst] ~= 1) then
        ret = false break
      end
      tbl[dst] = 2
    end
  end end
  return painted and ret
end

local isok = false
for i = 0, h - 1 do for j = 1 - w, w - 1 do
  if(i ~= 0 or 0 < j) then
    if(check(i, j)) then
      isok = true
      break
    end
  end
end end
print(isok and "YES" or "NO")