class MyStack {
    //定義一個佇列
    Queue<Integer> queue = new LinkedList<>();
    /** Initialize your data structure here. */
    public MyStack() {

    }
    
    /** Push element x onto stack. */
    //佇列是先進先出，棧為先進後出，用佇列模擬棧時，新增一個元素是在佇列的末尾，彈出一個元素是在隊頭
    //此時把該元素前面的元素全部出隊，該元素就到了隊首，其餘元素再進隊，即為一個棧先進後出的順序
 

    public void push(int x) {
        queue.add(x);
        int count = queue.size();
        while(count > 1){
            queue.add(queue.remove());
            count--;
        }
    }
    
    /** Removes the element on top of the stack and returns that element. */
    public int pop() {
        
 
return queue.remove();
    }
    
    /** Get the top element. */
    public int top() {
        return queue.peek();
    }
    
    /** Returns whether the stack is empty. */
    public boolean empty() {
        return queue.isEmpty();
    }
}

/**
 * Your MyStack object will be instantiated and called as such:
 * MyStack obj = new MyStack();
 * obj.push(x);
 * int param_2 = obj.pop();
 * int param_3 = obj.top();
 * boolean param_4 = obj.empty();
 
 
*/