{
    (n0)(n1)(n_add)
        /(b_to_nx)
            (b)
                /(zq)(lb)(hb!)
                    /
                        /
                            { /[hb!][b_to_nx] | hn }
                            /
                                [hn]
                            /
                                [hn]
                            [n_add]
                        /
                            /
                                [n0]
                            /
                                [n1]
                            [lb]
                        [n_add]
                    /
                        [n0]
                    [zq]
                [b]
        [YC]
|
    _b_to_n
}