import Control.Monad

main = do
  s <- getLine
  let [h,w] = map (read ::String->Int) $ words s in
    if h /= 0 && w /= 0 then do
      forM_ [1..h] $ \ i ->
        putStrLn $ take w $ cycle (if (i `mod` 2) == 1 then "#." else ".#")
      putStrLn ""
      main
    else
      return ()