main = readAndDo

readAndDo = do
  line <- getLine
  if line == "0 0" then return ()
  else do
    let [a, b] = input line
    solve [0..a-1] b
    putStrLn ""
    readAndDo

-- 入力
input :: String -> [Int]
input = (map read) . words

-- 解答
solve [] b = return ()
solve (a:xs) b = do
  putStrLn $ foldr (++) "" $ map (flip a) $ [0..b-1]
  solve xs b
  where
    flip y x | y `mod` 2 == 0 && x `mod` 2 == 0 = "#"
             | y `mod` 2 == 0 && x `mod` 2 == 1 = "."
             | y `mod` 2 == 1 && x `mod` 2 == 0 = "."
             | y `mod` 2 == 1 && x `mod` 2 == 1 = "#"


