import Text.Printf
main = do
  str<-getLine
  let [h,w]=map read $ words $ str::[Int]
  if(h==0 && w==0)
  then return ()
  else do
    putStrLn $ concat.(map (++"\n")) $ [["#."!!(mod (x+y) 2)|x<-[1..w]] | y<-[1..h]]
    main