loop do
  h,w = gets.chomp.split.map(&:to_i)
  break if h == 0 && w == 0
  count_h = 0
  count_w = 0
  h.times{
    w.times{
      if count_w % 2 == 0 || count_w == 0
        print "#"
      else
        print "."
      end
      count_w += 1
     }

     if count_h % 2 == 0 || count_h == 0
       count_w = 1
     else
       count_w = 0
     end
     count_h += 1
    puts
   }
   puts
end

