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class Stack {
public:
    vector<int> stack;
    // Push element x onto stack.
    void push(int x) {
        stack.push_back(x);
    }

    // Removes the element on top of the stack.
    void pop() {
        stack.pop_back();
    }

    // Get the top element.
    int top() {
        return stack[stack.size() - 1];
    }

    // Return whether the stack is empty.
    bool empty() {
        return stack.empty();        
    }
};