template <class A, class B>
ostream & operator<<(ostream &o, const pair<A,B> &d) {
return o << "<" << d.first << "," << d.second << ">";
template <class A, class B>
ostream & operator<<(ostream &o, const pair<A,B> &d) {
return o << "<" << d.first << "," << d.second << ">";