let rec print h w n =
        let rec print_s w n =
                match n with
                |0 -> Printf.printf "\n"
                |_ -> if (w - n) mod 2 = 0 then
                        begin
                                Printf.printf "#";
                                print_s w (n - 1)
                        end
                else
                        begin
                                Printf.printf ".";
                                print_s w (n - 1)
                        end
        in
        let rec print_d w n =
                match n with
                |0 -> Printf.printf "\n"
                |_ -> if (w - n) mod 2 = 0 then
                        begin
                                Printf.printf ".";
                                print_d w (n - 1)
                        end
                else
                        begin
                                Printf.printf "#";
                                print_d w (n - 1)
                        end
        in
        match n with
        |0 -> Printf.printf "\n"
        |_ -> if (h - n) mod 2 = 0 then
                begin
                        print_s w w;
                        print h w (n - 1)
                end
        else
                begin
                        print_d w w;
                        print h w (n - 1)
                end;;

let rec loop () =
        Scanf.scanf "%d %d\n" (fun h w -> if h = 0 && w = 0 then () else (print h w h;loop()));;

let () = loop ();;