module Main where

import Data.Functor

main :: IO ()
main =  do
 { [h,w] <- getInts
 ; if h == 0 && w == 0 then done
   else putStrLn (unlines (chessboard h w)) >> main
 }

chessboard :: Int -> Int -> [String]
chessboard h w = map (take w) $ take h $ cycle [cycle "#.", cycle ".#"]

done :: IO ()
done = return ()

getInts :: IO [Int]
getInts = map read . words <$> getLine