//mystk7.h --- CopyLeft by tsaiwn@csie.nctu.edu.tw
// --- implement a Stack using <list>  in C++ STL class library
#include <list>
using namespace std;
template <class T>
class MyStack {
   list <T> x;
public:
   void push(const T& y) {
      x.push_front(y);
   }
   T top( ) {
     return x.front( );
   }
   void pop( ) {
     x.pop_front( );
   }
   bool empty( ) { return x.begin() == x.end(); }
};