h, w = gets.split.map(&:to_i)

s = []
h.times {s << gets.chomp}

l = Array.new(h){Array.new(w)}
r = Array.new(h){Array.new(w)}
u = Array.new(h){Array.new(w)}
d = Array.new(h){Array.new(w)}

h.times do |i|
    xi = h - i - 1
    w.times do |j|
        xj = w - j - 1

        if s[i][j] == "#"
            l[i][j] = u[i][j] = 0
        else
            l[i][j] = j == 0 ? 1 : l[i][j - 1] + 1
            u[i][j] = i == 0 ? 1 : u[i - 1][j] + 1
        end

        if s[xi][xj] == "#"
            r[xi][xj] = d[xi][xj] = 0
        else
            r[xi][xj] = j == 0 ? 1 : r[xi][xj + 1] + 1
            d[xi][xj] = i == 0 ? 1 : d[xi + 1][xj] + 1
        end
    end
end

ans = 0
h.times do |i|
    w.times do |j|
        x = l[i][j] + r[i][j] + u[i][j] + d[i][j]
        ans = x if ans < x
    end
end

puts ans - 3