template <typename T>
class stos
{
    private:
        T key;
        stos <T> * next;
    public:
        bool emp() {return this->next==NULL;}
        stos() {this->next=NULL;}
        void pop();
        T top() {return this->next->key;}
        void push(T obj);
};
template <typename T>
void stos<T>::pop()
{
    stos <T> * tmp=this->next;
    this->next=this->next->next;
    delete tmp;
}
template <typename T>
void stos<T>::push(T obj)
{
    stos <T> * tmp=new stos<T>;
    tmp->next=this->next;
    tmp->key=obj;
    this->next=tmp;
}