template <class T> ostream& operator << (ostream& o, const vector <T>& v) {o << "{"; FOREACH(it, v) o << *it << ","; return o << "}";}
template <class A, class B> ostream& operator << (ostream& o, const pair <A, B>& p) {o << "("; o << p.first << "," << p.second << ")"; return o;}