h, w = gets.split.map(&:to_i)
sl = Array.new(h + 1).map{Array.new(w + 1, 0)}
su = Array.new(h + 1).map{Array.new(w + 1, 0)}
1.upto(h) do |i|
  c = 0
  b = gets
  1.upto(w) do |j|
    if b[j - 1] == '.'
      c += 1
      sl[i][j] = c
    elsif c > 0
      c = 0
    end
    if j == w && c > 0
      sl[i][j] = c
    end
  end
end
1.upto(h) do |i|
  c = 0
  w.downto(1) do |j|
    if c == 0 && sl[i][j] != 0
      c = sl[i][j]
    elsif sl[i][j] != 0
      sl[i][j] = c
    elsif c > 0
      c = 0
    end
  end
end
1.upto(w) do |j|
  c = 0
  1.upto(h) do |i|
    if sl[i][j] != 0
      c += 1
      su[i][j] = c
    elsif c > 0
      c = 0
    end
    if j == h && c > 0
      su[i][j] = c
    end
  end
end
1.upto(w) do |j|
  c = 0
  h.downto(1) do |i|
    if c == 0 && su[i][j] != 0
      c = su[i][j]
    elsif su[i][j] != 0
      su[i][j] = c
    elsif c > 0
      c = 0
    end
  end
end
ans = 0
1.upto(h) do |i|
  1.upto(w) do |j|
    ans = sl[i][j] + su[i][j] if ans < sl[i][j] + su[i][j]
  end
end
puts ans - 1