import           Control.Applicative
import           Data.Functor

main :: IO ()
main = do
  [h,w] <- fmap read . words <$> getLine
  if (h,w) == (0,0)
    then pure ()
    else printChessboard h w >> main

printChessboard :: Int -> Int -> IO ()
printChessboard h w = putStrLn chessboard
  where
    chessboard :: [Char]
    chessboard = unlines $ chunksOf w $ do
      i <- [1..h]
      j <- [1..w]
      pure $ if even (i+j)
             then '#'
             else '.'

chunksOf :: Int -> [a] -> [[a]]
chunksOf n l
  | n >= length l = [l]
  | otherwise = take n l : chunksOf n (drop n l)

