main = do
  [h, w] <- fmap (map read . words) getLine :: IO [Int]
  if [h, w] == [0, 0] then
    return ()
  else do
    mapM_ putStrLn [[ if y `mod` 2 == x `mod` 2 then
                        '#' else '.' | x <- [1..w]] | y <- [1..h]]
    putStrLn ""
    main