def chess(h, w)
  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"
end

loop {
  h, w = gets.split(" ").map(&:to_i)
  if h == 0 && w == 0
    break
  end
  chess(h, w)
}