while true
  h, w = gets.chomp.split.map(&:to_i)
  break if h == 0 && w == 0
  for i in 1..h
    if i % 2 == 0
      w.times do |j|
        if j % 2 == 0
          print "."
        else
          print "#"
        end
      end
      print "\n"
    else
      w.times do |j|
        if j % 2 == 0
          print "#"
        else
          print "."
        end
      end
      print "\n"
    end
  end
  print "\n"
end