
loop do
    h, w = gets.split(" ").map(&:to_i)

    if h == 0 && w == 0 then
        break;
    end
    
    h.times do |i|
        s = "#."

        w.times do |j|
            print s[(i + j) % 2]
        end

        print "\n"
    end
    
    print "\n"
end

