while true
  h,w = gets.split.map{ |e| e.to_i}
  break if (h == 0 && w == 0)
  even_line = ""
  odd_line = ""
  for i in 0..w-1
    if i.even?
      even_line += "#"
      odd_line += "."
    else
      even_line += "."
      odd_line += "#"
    end
  end
  
  
  h.times { |i|
    if (i.even?)
      puts even_line
    else
      puts odd_line
    end
  }
  puts ""
end