H, W = gets.split.map(&:to_i)
S = H.times.map { gets.chomp }

row_cnt = Array.new(H) { Array.new(W, 0) }
col_cnt = Array.new(H) { Array.new(W, 0) }

sh = '#'.freeze

H.times do |h|
  cnt = 0
  s = S[h]
  rc = row_cnt[h]
  W.times do |w|
    if s[w] == sh
      if cnt > 0
        (w - cnt).upto(w-1) do |i|
          rc[i] = cnt
        end
        cnt = 0
      end
    else
      cnt += 1
    end
  end
  if cnt > 0
    (W-1-cnt).upto(W-1) do |i|
      rc[i] = cnt
    end
  end
end

W.times do |w|
  cnt = 0
  H.times do |h|
    if S[h][w] == sh
      if cnt > 0
        (h-cnt).upto(h - 1) do |hh|
          col_cnt[hh][w] = cnt
        end
        cnt = 0
      end
    else
      cnt += 1
    end
  end

  if cnt > 0
    (H-1-cnt).upto(H - 1) do |hh|
      col_cnt[hh][w] = cnt
    end
  end
end

ans = 0
H.times do |h|
  cc = col_cnt[h]
  rc = row_cnt[h]
  W.times do |w|
    sum = cc[w] + rc[w] - 1
    ans = sum if sum > ans
  end
end

puts ans
