typedef struct STnode* link;
struct STnode { Item item; link* next; int sz; };
static link head, z;
static int N, lgN;
link NEW(Item item, int k)
  { int i; link x = malloc(sizeof *x);
    x->next = malloc(k*sizeof(link));
    x->item = item; x->sz = k;
    for (i = 0; i < k; i++) x->next[i] = z;
    return x;
  }
void STinit(int max)
  {
    N = 0; lgN = 0;
    z = NEW(NULLitem, 0);
    head = NEW(NULLitem, lgNmax);
  }
-----
int randX()
  { int i, j, t = rand();
    for (i = 1, j = 2; i < lgNmax; i++, j += j)
      if (t > RAND_MAX/j) break;
    if (i > lgN) lgN = i;
    return i;
  }
void insertR(link t, link x, int k)
  { Key v = key(x->item);
    if (less(v, key(t->next[k]->item)))
      {
        if (k < x->sz)
          { x->next[k] = t->next[k];
            t->next[k] = x; }
        if (k == 0) return;
        insertR(t, x, k-1); return;
      }
    insertR(t->next[k], x, k);
  }
void STinsert(Key v)
  { insertR(head, NEW(v, randX()), lgN); N++; }
-----
void deleteR(link t, Key v, int k)
  { link x = t->next[k];
    if (!less(key(x->item), v))
      {
        if (eq(v, key(x->item)))
          { t->next[k] = x->next[k]; }
        if (k == 0) { free(x); return; }
        deleteR(t, v, k-1); return;
      }
    deleteR(t->next[k], v, k);
  }
void STdelete(Key v)
  { deleteR(head, v, lgN); N--; }