template<typename T>
struct IdPool {
    map<T, int> idmap;
    vector<T> items;
    void clear() { idmap.clear(); items.clear(); }
    int getid(const T &t) {
        auto it = idmap.find(t);
        if (it != idmap.end()) return it->second;
        int ans = items.size(); items.push_back(t); idmap[t] = ans; return ans;
    }
    T& operator[](int i) { return items[i]; }
    int size() { return items.size(); }
};
IdPool<int> idp;