def line(w, x, y)
    l = ""
    w.times do |i|
        if i.even?
            l += x
        else
            l +=y
        end
    end
    puts ""
end

loop do
    h, w = gets.chomp.split.map(&:to_i)
    if h == 0 && w == 0
        break
    end
    h.times do |i|
        if i.even?
            line(w, "#", ".")
        else
            line(w, ".", "#")
        end
    end
    puts ""
end