assert (k > 0);
while (--k > 0)
  {
    struct rtavl_node *y = pa[k];

    if (da[k] == 0)
      {
        y->rtavl_balance++;
        if (y->rtavl_balance == +1)
          break;
        else if (y->rtavl_balance == +2)
          {
            struct rtavl_node *x = y->rtavl_link[1];

            assert (x != NULL);
            if (x->rtavl_balance == -1)
              {
                struct rtavl_node *w;

                assert (x->rtavl_balance == -1);
                w = x->rtavl_link[0];
                x->rtavl_link[0] = w->rtavl_link[1];
                w->rtavl_link[1] = x;
                y->rtavl_link[1] = w->rtavl_link[0];
                w->rtavl_link[0] = y;
                if (w->rtavl_balance == +1)
                  x->rtavl_balance = 0, y->rtavl_balance = -1;
                else if (w->rtavl_balance == 0)
                  x->rtavl_balance = y->rtavl_balance = 0;
                else /* |w->rtavl_balance == -1| */
                  x->rtavl_balance = +1, y->rtavl_balance = 0;
                w->rtavl_balance = 0;
                if (y->rtavl_link[1] == NULL)
                  {
                    y->rtavl_rtag = RTAVL_THREAD;
                    y->rtavl_link[1] = w;
                  }
                if (w->rtavl_rtag == RTAVL_THREAD)
                  {
                    x->rtavl_link[0] = NULL;
                    w->rtavl_rtag = RTAVL_CHILD;
                  }
                pa[k - 1]->rtavl_link[da[k - 1]] = w;
              }
            else
              {
                pa[k - 1]->rtavl_link[da[k - 1]] = x;
                if (x->rtavl_balance == 0)
                  {
                    y->rtavl_link[1] = x->rtavl_link[0];
                    x->rtavl_link[0] = y;
                    x->rtavl_balance = -1;
                    y->rtavl_balance = +1;
                    break;
                  }
                else /* |x->rtavl_balance == +1| */
                  {
                    if (x->rtavl_link[0] != NULL)
                      y->rtavl_link[1] = x->rtavl_link[0];
                    else
                      y->rtavl_rtag = RTAVL_THREAD;
                    x->rtavl_link[0] = y;
                    y->rtavl_balance = x->rtavl_balance = 0;
                  }
              }
          }
      }
    else
      {
        y->rtavl_balance--;
        if (y->rtavl_balance == -1)
          break;
        else if (y->rtavl_balance == -2)
          {
            struct rtavl_node *x = y->rtavl_link[0];

            assert (x != NULL);
            if (x->rtavl_balance == +1)
              {
                struct rtavl_node *w;

                assert (x->rtavl_balance == +1);
                w = x->rtavl_link[1];
                x->rtavl_link[1] = w->rtavl_link[0];
                w->rtavl_link[0] = x;
                y->rtavl_link[0] = w->rtavl_link[1];
                w->rtavl_link[1] = y;
                if (w->rtavl_balance == -1)
                  x->rtavl_balance = 0, y->rtavl_balance = +1;
                else if (w->rtavl_balance == 0)
                  x->rtavl_balance = y->rtavl_balance = 0;
                else /* |w->rtavl_balance == +1| */
                  x->rtavl_balance = -1, y->rtavl_balance = 0;
                w->rtavl_balance = 0;
                if (x->rtavl_link[1] == NULL)
                  {
                    x->rtavl_rtag = RTAVL_THREAD;
                    x->rtavl_link[1] = w;
                  }
                if (w->rtavl_rtag == RTAVL_THREAD)
                  {
                    y->rtavl_link[0] = NULL;
                    w->rtavl_rtag = RTAVL_CHILD;
                  }
                pa[k - 1]->rtavl_link[da[k - 1]] = w;
              }
            else
              {
                pa[k - 1]->rtavl_link[da[k - 1]] = x;
                if (x->rtavl_balance == 0)
                  {
                    y->rtavl_link[0] = x->rtavl_link[1];
                    x->rtavl_link[1] = y;
                    x->rtavl_balance = +1;
                    y->rtavl_balance = -1;
                    break;
                  }
                else /* |x->rtavl_balance == -1| */
                  {
                    if (x->rtavl_rtag == RTAVL_CHILD)
                      y->rtavl_link[0] = x->rtavl_link[1];
                    else
                      {
                        y->rtavl_link[0] = NULL;
                        x->rtavl_rtag = RTAVL_CHILD;
                      }
                    x->rtavl_link[1] = y;
                    y->rtavl_balance = x->rtavl_balance = 0;
                  }
              }
          }
      }
  }
