def line(w, f, s)
    w.times do |i|
        if i.even?
            print f
        else
            print s
        
    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

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