import Data.Map hiding (map)
import Data.Maybe
import Control.Monad
import Prelude hiding (lookup,null)

type Board = Map (Int,Int) (Maybe Bool)
test1 = concat
 ["######...\n",
  "#.####.#.\n",
  "######...\n"]

test2 = concat
  ["..............##................\n",
   "..........##########............\n",
   "......##################........\n",
   "..##########################....\n",
   "##....##################....##..\n",
   "######....##########....######..\n",
   "##########....##....##########..\n",
   "##....########..##############..\n",
   "######....####..##############..\n",
   "##############..##############..\n",
   "##############..##############..\n",
   "##############..##############..\n",
   "..############..############....\n",
   "......########..########........\n",
   "..........####..####............\n",
   "..............##................\n"]

main = do
  [m,n] <- map read . words <$> getLine :: IO [Int]
  c <- getContents
  putStrLn $ if isSeparatable (m,n) (genBoard c) then "YES" else "NO"

genBoard :: String -> Board
genBoard = gBRow 0 . lines
  where
    gBRow _ [] = empty
    gBRow n (line:ls) = gBCol (gBRow (n+1) ls) (n,0) line

    gBCol b _ [] = b
    gBCol b (n,m) (square:ss) =
     if square=='#'
       then insert (n,m) Nothing b'
       else b'
       where
         b' = gBCol b (n,m+1) ss

showBoard :: (Int,Int) -> Board -> String
showBoard (n,m) b = sBRow 0
  where
    sBRow n' | n'<n = sBCol (n',0) ++ sBRow (n'+1)
             | otherwise = []

    sBCol pos@(n',m') | m'<m =
      case lookup pos b of
        Nothing -> '.':rest
        Just Nothing ->  '#':rest
        Just (Just True) -> 'X':rest
        Just (Just False) -> 'O':rest
                      | otherwise = "\n"
      where
        rest = sBCol (n',m'+1)

colorBoard :: (Int,Int) -> Board -> Maybe Board
colorBoard (m,n) b = cB b $ keys b
  where
    cB b' [] = Just b'
    cB b' ((m',n'):ps) =
      case b'!(m',n') of
        Nothing ->
          case lookup (m'+m,n'+n) b' of
            Just Nothing -> cB (insert (m'+m,n'+n) (Just False) $ insert (m',n') (Just True) b') ps
            _ -> Nothing
        Just False -> cB b' ps

isSeparatable :: (Int,Int) -> Board -> Bool
isSeparatable (m,n) b = (&&) (not $ null b) $ or $ isJust <$> (colorBoard <$> [(x,y)|x<-[0..m],y<-[-n..n],x/=0||y/=0] <*> [b])
--isSeparatable (m,n) b = (||) (null b) $ or $ isJust <$> (colorBoard <$> (tail [(x,y)|x<-[0..m],y<-[-n..n]] ++ [(x,y)|x<-[0..m],y<-[-1..(-n)]]) <*> [b])