h_arr = []
w_arr = []
while true
  h, w = gets.split.map(&:to_i)
  break if h == 0 && w == 0
  h_arr.push(h)
  w_arr.push(w)
end

h_arr.zip(w_arr) do |h, w|
  num = 1
  w_num = 1
  h.times do
    w.times do
      if w_num % 2 == 1
        if num % 2 == 1
          print "#"
        else
          print "."
        end
      else
        if num % 2 == 1
          print "."
        else
          print "#"
        end
      end
      num = num + 1
    end
    w_num = w_num + 1
    puts ""
  end
  puts ""
end

