import Control.Applicative

createRows :: Int -> Int -> Int -> [String]
createRows n h w
    | n > h          = []
    | n `mod` 2 == 1 = (take w . concat $ repeat "#.") : createRows (n + 1) h w
    | otherwise      = (take w . concat $ repeat ".#") : createRows (n + 1) h w

main :: IO()
main = do
    args <- (map (read :: String -> Int) . words) <$> getLine
    if (args == [0, 0])
    then return ()
    else do
        (putStrLn . unlines) $ createRows 1 (args !! 0) (args !! 1)
        main