lines = STDIN.read.split("\n")
lines.each do |line|
  h, w = line.split(" ").map(&:to_i)
  break if h == 0 && w == 0
  h.times do |i|
    w.times do |j|
      if (i + j) % 2 == 0
        print "#"
      else
        print "."
      end
    end
    print "\n"
  end
  print "\n"
end