pattern = [ %w|# .|, %w|. #| ]

loop do

  h, w = gets.split.map(&:to_i)
  exit if h + w == 0

  for i in 0...h do
    pat = pattern[ ( i % 2 ) ] # initial pattern
    for j in 0...w do
      print pat[ ( j % 2 ) ]
    end
    puts
  end
  puts

end