import Data.Functor ((<$>))

main :: IO ()
main = do
  [h, w] <- map (read :: String -> Int) . words <$> getLine
  if h == 0 && w == 0
    then return ()
    else do
      let xs = take w $ cycle "#."
          ys = take w $ cycle ".#"
      putStrLn . unlines $ take h $ cycle [xs,ys]
      main

