#1:??¶??°???????\???°??????????????????def??§????????????????\???°?????????/2 +???????????°????????????
=begin
def even
    (h / 2).times do
        puts = "#." * (w / 2)
        puts = ".#" * (w / 2)
    end
end
def odd
    (h / 2).times do
        puts = "#." * w
        puts = ".#" * w
end
=end
def line(w, f, s)
    w.times do |i|
        if i.even?
            print f
        else
            print s
        end
    end
    puts ""
end

loop do
    h, w = gets.chomp.split.map(&:to_i)
    break if h==0 && w==0

    h.times do |i|
        if (i % 2) == 0
            line(w, "#", ".")
        else
            line(w, ".", "#")
        end
    end
    puts ""
end