main :: IO()
main = do
  inputs <- getContents
  let specs = takeWhile (/= [0, 0]) $ [ map (\x -> read x ::Int) ws | ws <- map words $ lines inputs]
  mapM_ drawCheck specs


drawCheck :: [Int] -> IO ()
drawCheck [h, w] = do
  mapM_ (\x -> drawNthLine x w) [1..h]
  putStrLn ""

drawNthLine :: Int -> Int-> IO ()
drawNthLine n w = do
  let [e, o] = case even n of {True -> ['.', '#']; False -> ['#','.']}
  putStrLn $ map (\x -> case even x of {True -> o; False -> e}) [1..w]