while (h, w = gets.split.map(&:to_i)) != [0, 0]
  g = []
  h.times do
    g << gets.chop.split("")
  end
  s = []
  (0...w).each do |x|
    (0...h).each do |y|
      (x...w).each do |a|
        (y...h).each do |b|
          f = true
          (x..a).each do |i|
            (y..b).each do |j|
              if g[j][i] != ?.
                f = false
                break
              end
            end
          end
          if f
            s << ((a - x + 1)*(b - y + 1))
          end
        end
      end
    end
  end
  p s.max
end