# Print a Chessboard
loop do
    h, w, = gets.split.map(&:to_i)
    break if h == 0 && w == 0
    h.times do |n|
        if n.even?
            puts ('#.' * w)[0,w]
        else
            puts ('.#' * w)[0,w]
        end
    end
    puts
end