class Set {
    private:
        std::vector<int> _vec;  // vector to store the integers
        int _evens;             // number of even integers in the set
    public:
        Set();
        void putIn(int e);      // put an integer in - check if it's already there and increase _evens if the number is even
        void deleteItem(int e); // delete an integer from the set
        bool isIn(int e);       // check if e is in the set
        int getEvens();         // get the number of even numbers - stored in _evens
        void print();           // print the integers stored in set

        friend std::ostream& operator<< (std::ostream& s, const Set& a);
};