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

l = Array.new(H) { Array.new(W, 0) }
r = Array.new(H) { Array.new(W, 0) }
u = Array.new(H) { Array.new(W, 0) }
d = Array.new(H) { Array.new(W, 0) }

max = 0
a1 = (0..H-1).to_a
a1r = a1.reverse
a2 = (0..W-1).to_a
a2r = a2.reverse

a1.product(a2) do |i,j|
  if s[i][j] == "#"
    l[i][j] = 0
  else
    l[i][j] = (j == 0) ? 1 : l[i][j-1] + 1
  end
end
a1.product(a2r) do |i,j|
  if s[i][j] == "#"
    r[i][j] = 0
  else
    r[i][j] = (j == W-1) ? 1 : r[i][j+1] + 1
  end
end
a1.product(a2) do |i,j|
  if s[i][j] == "#"
    u[i][j] = 0
  else
    u[i][j] = (i == 0) ? 1 : u[i-1][j] + 1
  end
end
a1r.product(a2) do |i,j|
  if s[i][j] == "#"
    d[i][j] = 0
  else
    d[i][j] = (i == H-1) ? 1 : d[i+1][j] + 1
  end
end
a1.product(a2) do |i,j|
  c = l[i][j] + r[i][j] + u[i][j] + d[i][j] - 3
  max = c if c > max
end

puts max