import Data.List

f3 :: String -> String
f3 str
   |((head str)=='#') && ((length str)>1) =replicate (length str) 'b'
   |otherwise=str

f2 ::String->String
f2 str=concat $ map f3 $ group str


f :: [String]->[String]
f []=[]
f (x:xs)=f2 x : f xs

main = do
      x<-getLine
      y<-getContents
      let z=lines y
          z2=transpose z
          z3=f z
          z4=transpose (f z2)
          (h:w:[])=map read (words x)::[Int]
      putStrLn $ if (length [1 | y<-[0..(h-1)],x<-[0..(w-1)],z !! y !! x=='#',z3 !! y !! x=='#',z4 !! y !! x=='#'])>0 then "No" else "Yes"