while true
  h,w = gets.split.map(&:to_i)
 break if h == 0 && w ==0
     
   h.times do |n|
      if n % 2 == 0
         puts (`#.`*w)[0,w]
     else
        puts(`.#`*w)[0,w]
     end
  end
  puts
  end
  