In file included from main.cpp:6:
./leftist_heap.hpp:25:25: error: a non-type template parameter cannot have type 'Pair'
template <typename T, T MIN_INF, class Compare = std::less <T> >
                        ^
main.cpp:36:5: note: while substituting prior template arguments into non-type template parameter 'MIN_INF' [with T = Pair]
    LeftistHeap<Pair, Pair()> queue;
    ^~~~~~~~~~~~~~~~~~~~~~~~~