h, w = gets.chomp.split(' ').map(&:to_i)
grid = []
h.times do
  grid << gets.chomp.split('')
end
yoko = []
(0...h).each do |i|
  tmp_yoko = []
  count_yoko = 0
  (0...w).each do |j|
    if grid[i][j] == '.'
      count_yoko += 1
    else
      tmp_yoko += Array.new(count_yoko, count_yoko)
      tmp_yoko += [0]
      count_yoko = 0
    end
  end
  tmp_yoko += Array.new([1, count_yoko].max, count_yoko) if count_yoko > 0
  yoko << tmp_yoko
end
tate = []
(0...w).each do |i|
  tmp_tate = []
  count_tate = 0
  (0...h).each do |j|
    if grid[j][i] == '.'
      count_tate += 1
    else
      tmp_tate += Array.new(count_tate, count_tate)
      tmp_tate += [0]
      count_tate = 0
    end
  end
  tmp_tate += Array.new([1, count_tate].max, count_tate) if count_tate > 0
  tate << tmp_tate
end
max = 0
(0...h).each do |i|
  (0...w).each do |j|
    max = [max, tate[j][i] + yoko[i][j]].max
  end
end
puts max > 0 ? max - 1 : max