#include <iostream>

using namespace std;


class CustomStack {
        public:
        void Stack() {
            i = 0;
        };

        int size() const{
            return i;
        }

        int top(){
            return mData[i - 1];
        }

        void push(int elem){
            mData[i] = elem;
            ++i;
        }

        void pop(){
            --i;
        }

        bool empty() const{
            if (i == 0) return true;
            return false;
        }

        void extend(int n){
            i += n;
        }

        private:
        int mData[100];
        int i;
};


int main() {
    CustomStack Stack{};

    cout << Stack.empty();

    Stack.push(123);
    Stack.push(342);
    Stack.push(321);
    Stack.push(324);


    cout << Stack.size() << endl;
    cout << Stack.empty() << endl;
    Stack.extend(5);
    cout << Stack.empty() << endl;

    Stack.extend(-5);

    cout << Stack.top() << endl;
    Stack.pop();
    cout << Stack.top() << endl;


    return 0;
}