module Main where

import Control.Monad
ok :: (Int,Int) -> (Int,Int) -> [[Char]] -> Bool
ok (x,y) (h,w) s =
    if s !! y !! x == '.'
        then True
        else if (x == 0) && (y == 0)
            then True 
            else if x == 0 && y > 0
                then (s !! (y-1) !! x == '.')
                else if y == 0 && x > 0
                    then (s !! y !! (x-1) == '.')
                    else (s !! (y-1) !! (x-1) == '.')

main :: IO ()
main = do
    [h,w] <- (map read . words) <$> getLine 
    s <- replicateM h <$> getLine 
    if and [and [ok (i,j) (h,w) s | i <- [0..w-1]] | j <- [0..h-1]]
            then putStrLn "Yes"
            else putStrLn "No"
    return()