str = "#." * 150
ARGF.each_line do |line|
  chess = ""
  h, w = line.split.map(&:to_i)
  break if h == 0 && w == 0
  (0...h).each do |i|
    odd = i % 2
    chess += str[odd..(w + odd)] + "\n"
  end
  puts chess + "\n"
end