h, w = gets.chomp.split.map(&:to_i)
a = []
0.step(h-1) do
  a << gets.chomp
end

ary = Array.new(h) { Array.new(w) }
ary_2 = Array.new(h) { Array.new(w) }

m = 'a'
num = {}
num['zero'] = 0
tmp = 0

0.step(h-1) do |gyo|
  tmp = 0
  0.step(w-1) do |retsu|
    if a[gyo][retsu] == '.'
      tmp += 1
      ary[gyo][retsu] = m
    else
      ary[gyo][retsu] = 'zero'
      num[m] = tmp
      tmp = 0
      m = m.succ
    end
  end
  if tmp > 0
    num[m] = tmp
    m = m.succ
    tmp = 0
  end
end

0.step(w-1) do |retsu|
  tmp = 0
  0.step(h-1) do |gyo|
    if a[gyo][retsu] == '.'
      tmp += 1
      ary_2[gyo][retsu] = m
    else
      ary_2[gyo][retsu] = 'zero'
      num[m] = tmp
      tmp = 0
      m = m.succ
    end
  end
  if tmp > 0
    num[m] = tmp
    m = m.succ
    tmp = 0
  end
end

max = 0
t = 0
0.step(w-1) do |retsu|
  0.step(h-1) do |gyo|
    t = num[ary[gyo][retsu]] + num[ary_2[gyo][retsu]]
    max = t if t > max
  end
end

p max - 1