local h, w = io.read("*n", "*n", "*l")
local t = {}
local s_sharp = string.byte("#")
for i = 1, h do
  local s = io.read()
  for j = 1, w do
    local idx = (i - 1) * w + j
    t[idx] = s:byte(j) ~= s_sharp
  end
end
local score = {}
for i = 1, h * w do score[i] = 0 end
local len = 0
local function func(idx)
  score[idx] = score[idx] + len
  if t[idx] then len = len + 1
  else len = 0
  end
end
for i = 1, h do
  len = 0
  for j = 1, w do
    func((i - 1) * w + j)
  end
end
for i = 1, h do
  len = 0
  for j = w, 1, -1 do
    func((i - 1) * w + j)
  end
end
for j = 1, w do
  len = 0
  for i = 1, h do
    func((i - 1) * w + j)
  end
end
for j = 1, w do
  len = 0
  for i = h, 1, -1 do
    func((i - 1) * w + j)
  end
end
local ret = 0
local mma = math.max
for i = 1, h * w do
  if t[i] then
    ret = mma(ret, score[i])
  end
end
print(ret + 1)
