/*
 * This code is from "Algorithms in C, Third Edition,"
 * by Robert Sedgewick, Addison Wesley Longman, 1998.
 */
Item selectR(link h, int k)
  { int t = h->l->N;
    if (h == z) return NULLitem;
    if (t > k) return selectR(h->l, k);
    if (t < k) return selectR(h->r, k-t-1);
    return h->item;
  }
Item STselect(int k)
  { return selectR(head, k); }