import Control.Applicative
import Control.Monad
import Data.List
main = do
    [h, w] <- (map read . words) <$> getLine
    printDataSet h w

printDataSet :: Int -> Int -> IO()
printDataSet 0 0 = putStr ""
printDataSet h w = do
    let flatBoard = intercalate "" $ replicate (h * w) "#."
    printChessBoard h w flatBoard
    putStrLn ""
    [h, w] <- (map read . words) <$> getLine
    printDataSet h w

printChessBoard :: Int -> Int -> String -> IO()
printChessBoard 0 _ _ = putStr ""
printChessBoard last width flatBoard
    | mod width 2 == 0 = do
        putStrLn $ take width flatBoard
        printChessBoard (last - 1) width $ drop (width + 1) flatBoard
    | otherwise = do
        putStrLn $ take width flatBoard
        printChessBoard (last - 1) width $ drop width flatBoard