while true
  h,w = gets.split.map(&:to_i)
  if h == 0 && w == 0 then break end
    arr = []
  w.times  do |i|
    if i == 0 || i.even?
      arr << "#"
    else
      arr << "."
    end
  end
   arr2 = arr.map{|x| x=="#" ? "." : "#"}.join
   arr = arr.join
  h.times do |i|
    if i == 0 || i.even?
      puts arr
    else
      puts arr2
    end
  end
    puts "\n"
end
