def pp(c)
    c.each do |l|
        puts l
    end
    puts
end
$dx = [0,1,0,-1]
$dy = [1,0,-1,0]
$m = Array.new
$mm = Array.new
w, h = gets.split.map(&:to_i)
c = h.times.map{gets.chomp}
bl = false
c.each_with_index do |line,i|
    line.each_char.with_index do |cc,j|
        next unless cc == "."
        q = [[i,j]]
        while q.size > 0
            sy, sx = q.shift
            c[sy][sx] = "a"
            $m.push([sy,sx])
            for i in 0..3
                cy = sy + $dy[i]
                cx = sx + $dx[i]
                if c[cy][cx] == "." && cy.between?(1,h-2) && cx.between?(1,w-2) && !q.include?([cy,cx])
                    q.push([cy,cx])
                end
            end
        end
        bl = true
        break
    end
    break if bl
end
bl = false
c.each_with_index do |line,i|
    line.each_char.with_index do |cc,j|
        next unless cc == "."
        q = [[i,j]]
        while q.size > 0
            sy, sx = q.shift
            c[sy][sx] = "b"
            $mm.push([sy,sx])
            for i in 0..3
                cy = sy + $dy[i]
                cx = sx + $dx[i]
                if c[cy][cx]=="." && cy.between?(1,h-2) && cx.between?(1,w-2) && !q.include?([cy,cx])
                    q.push([cy,cx])
                end
            end
        end
        bl = true
        break
    end
    break if bl
end
ret = Float::INFINITY
$m.each do |p|
    $mm.each do |pp|
        t = (p[0] - pp[0]).abs + (p[1] - pp[1]).abs - 1
        ret = t if t < ret
    end
end
p ret