H, W = gets.chomp.split.map(&:to_i)
G = []
H.times { G << gets.chomp }
ans = 0
l = Array.new(H).map{Array.new(W, 0)}
r = Array.new(H).map{Array.new(W, 0)}
u = Array.new(H).map{Array.new(W, 0)}
d = Array.new(H).map{Array.new(W, 0)}
H.times do |i|
  (W - 1).downto(0) do |j|
    next if G[i][j] == '#'

    if j == W - 1
      r[i][j] = 1
    else
      r[i][j] = r[i][j+1] + 1
    end
  end
  W.times do |j|
    next if G[i][j] == '#'

    if j == 0
      l[i][j] = 1
    else
      l[i][j] = l[i][j-1] + 1
    end
  end
end
W.times do |j|
  (H - 1).downto(0) do |i|
    next if G[i][j] == '#'

    if i == H - 1
      d[i][j] = 1
    else
      d[i][j] = d[i+1][j] + 1
    end
  end
  H.times do |i|
    next if G[i][j] == '#'
    if i == 0
      u[i][j] = 1
    else
      u[i][j] = u[i-1][j] + 1
    end
  end
end
H.times do |i|
  W.times do |j|
    next if G[i][j] == '#'
    num = l[i][j] + r[i][j] + u[i][j] + d[i][j] - 3
    ans = [ans, num].max
  end
end
puts ans