class Stack {
public:
    // Push element x onto stack.
    void push(int x) {
        q.push(x);
        for (int i=0; i<q.size()-1; i++) {
            q.push(q.front());
            q.pop();
        }
    }

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

    // Get the top element.
    int top() {
        return q.front();
    }

    // Return whether the stack is empty.
    bool empty() {
        return q.empty();
    }
private:
    queue<int> q;
};

class Queue {
public:
    // Push element x to the back of queue.
    void push(int x) {
        input.push(x);
    }

    // Removes the element from in front of queue.
    void pop(void) {
        peek();
        output.pop();
    }

    // Get the front element.
    int peek(void) {
        if (output.empty()) {
            while (!input.empty()) {
                output.push(input.top());
                input.pop();
            }
        }
        return output.top();
    }

    // Return whether the queue is empty.
    bool empty(void) {
        return input.empty() && output.empty();
    }
private:
    stack<int> input;
    stack<int> output;
};