loop{
h,w = gets.split.map(&:to_i)
if h == 0 && w == 0
    break
end
i = 0
h.times{
    i += 1
    if i.odd?
        if w.odd?
            puts "#." * (w / 2) + "#"
        elsif w.even?
            puts "#." * (w / 2)
        end
    elsif i.even?
        if w.odd?
            puts ".#" * (w / 2) + "."
        elsif w.even?
            puts ".#" * (w / 2)
        end
    end
}
puts ""
}
