h, w = gets.split.map(&:to_i)
s = $<.map(&:bytes).flatten

ww = w+1
mx = (h+1)*(w+1)

dph = Array.new(mx, 0)
dpw = Array.new(mx, 0)

(h*ww-1).downto(0) do |i|
    if s[i] == 46
        dph[i] = dph[i+ww] + 1
        dpw[i] = dpw[i+1] + 1
    end
end

ans = 0
(h*ww).times do |i|
    if s[i] == 46
        dph[i+ww] = dph[i]
        dpw[i+1] = dpw[i]
        res = dph[i] + dpw[i] - 1
        ans = res if ans < res
    end
end
puts ans