$w
$h
$a
$b
$c
$dx = [1, 0, -1, 0]
$dy = [0, 1, 0, -1]
$min = 10 ** 10
def checkRange(x, y)
    return x >= 0 && x < $w && y >= 0 && y < $h
end
def paint(cx, cy, v)
    $b[cy][cx] = true
    if $c[cy][cx] == "#"
        return
    end
    $a[cy][cx] = v
    4.times do |i|
        tx = cx + $dx[i]
        ty = cy + $dy[i]
        next if !checkRange(tx, ty) || $b[ty][tx]
        paint(tx, ty, v)
    end
end
$w, $h = gets.split.map(&:to_i)
$a = Array.new($h).map{ Array.new($w, 0) }
$b = Array.new($h).map{ Array.new($w, false) }
$c = Array.new($h)
$h.times do |i|
    $c[i] = gets.strip
end
v = 1
$h.times do |i|
    $w.times do |j|
        if $c[i][j] == "." && $a[i][j] == 0
            paint(j, i, v)
            v += 1
        end
    end
end
coord = Struct.new(:x, :y)
d = Array.new($h).map{ Array.new($w, false) }
ah = Array.new
bh = Array.new
$h.times do |i|
    $w.times do |j|
        if $a[i][j] != 0
            next
        end
        4.times do |k|
            tx = j + $dx[k]
            ty = i + $dy[k]
            next if !checkRange(tx, ty)
            if $a[ty][tx] == 1
                ah.push(coord.new(j, i))
            elsif $a[ty][tx] == 2
                bh.push(coord.new(j, i))
            end
        end
    end
end
min = 10 ** 10
ah.each do |a|
    bh.each do |b|
        v = (a.x - b.x).abs + (a.y - b.y).abs + 1
        min = v if v < min
    end
end
puts min