class cart_tree {
  typedef struct _Node {
    int x, y, cnt;
    _Node *l, *r;

    _Node(int _x) : x(_x), y((rand() << 16) ^ rand()), cnt(1), l(NULL), r(NULL) {}
    ~_Node() { delete l; delete r; }
    void recalc() {
      cnt = 1;
      if (l) cnt += l->cnt;
      if (r) cnt += r->cnt;
    }
  } *Node;

  Node merge(Node l, Node r) {
    if (!l || !r) return l ? l : r;
    if (l->y < r->y) {
      l->r = merge(l->r, r);
      l->recalc();
      return l;
    } else {
      r->l = merge(l, r->l);
      r->recalc();
      return r;
    }
  }

  void split(Node v, int x, Node &l, Node &r) {
    l = r = NULL;
    if (!v) return;
    if (v->x < x) {
      split(v->r, x, v->r, r);
      l = v;
    } else {
      split(v->l, x, l, v->l);
      r = v;
    }
    v->recalc();
  }

  Node root;
  public:
  cart_tree() : root(NULL) {}
  ~cart_tree() { delete root; }
  void insert(int x) {
    Node l, r;
    split(root, x, l, r);
    root = merge(merge(l, new _Node(x)), r);
  }
  void erase(int x) {
    Node l, m, r;
    split(root, x, l, m);
    split(m, x + 1, m, r);
    assert(m && m->cnt == 1 && m->x == x);
    delete m;
    root = merge(l, r);
  }
  int size() const { return root ? root->cnt : 0; }
};