main = do
    ss <- getLine
    let hw = map (\x -> read x :: Int) $ words ss
    let h = hw!!0
    let w = hw!!1
    if (h==0 && w==0)
        then return ()
        else do
            draw h w
            main

draw h w = drawBoard 1 h w

drawBoard i h w = do
    let line = if odd i then concat $ replicate 150 "#."
                        else concat $ replicate 150 ".#"
    if i>h
        then putStrLn ""
        else do
            putStrLn $ take w line
            drawBoard (i+1) h w
