loop do
  h, w = gets.split.map(&:to_i)
  break if h == 0 && w == 0
  
  evenChess = (0...w).map { |i| i.even? ? "#" : "." }.join
  oddChess = (0...w).map { |i| i.even? ? "." : "#" }.join
  
  h.times do |i|
      chess = i.even? ? evenChess : oddChess
      puts chess
  end
  puts
end