import Control.Applicative

import Control.Monad
    (when)

type Problem = (Int, Int)

type Result = [String]

check :: Int -> Int -> Char

check x y
    | even y
        = if even x then '#' else '.'
        
    | otherwise
        = if even x then '.' else '#'

solve :: Problem -> Result

solve (h, w)
    = [[check x y | x <- [0..(w - 1)]] | y <- [0..(h - 1)]]

input :: IO Problem

input
    = do
        [h, w] <- map read.words <$> getLine
        return (h, w)

output :: Result -> IO ()

output xs
    = putStrLn $ concat [x ++ "\n" | x <- xs]
    
main :: IO ()

main
    = do
        xs <- input
        when (xs /= (0, 0)) $ do
            output $ solve xs
            main