loop {
  h, w = gets.split(" ").map(&:to_i)
  if h == 0 && w == 0
    break
  end
  for i in 1..h
    for n in 1..w
      if (i+n)%2 == 1
        print "."
      else
        print "#"
      end
    end
    puts "\n"
  end
  puts "\n"
}