while (h, w = gets.split().map(&:to_i)) != [0, 0]
  if w % 2 == 0
    h.times{|i|
      puts i%2==0 ? "#."*(w/2) : ".#"*(w/2)
    }
  else
    for i in 0...h
      for j in 0...w
        if i % 2 == 0
          if j % 2 == 0 then print "#" else print "." end
        else
          if j % 2 == 0 then print "." else print "#" end
        end
      end
      puts
    end
  end
  puts
end