class MyQueue {
public:
    /** Initialize your data structure here. */
    stack<int> stk,cache;
    MyQueue() {

    }

    /** Push element x to the back of queue. */
    void push(int x) {
        stk.push(x);
    }

    //将a中的元素逆序放到b中，结束后a为空
    void copy(stack<int> &a,stack<int> &b){
        while(a.size()){
            b.push(a.top());
            a.pop();
        }
    }

    /** Removes the element from in front of queue and returns that element. */
    int pop() {
        copy(stk,cache);
        int x = cache.top();
        cache.pop();
        copy(cache,stk);
        return x;
    }

    /** Get the front element. */
    int peek() {
        copy(stk,cache);
        int x = cache.top();
        copy(cache,stk);
        return x;
    }

    /** Returns whether the queue is empty. */
    bool empty() {
        return stk.empty();
    }
};

/**
 * Your MyQueue object will be instantiated and called as such:
 * MyQueue obj = MyQueue();
 * obj.push(x);
 * int param_2 = obj.pop();
 * int param_3 = obj.peek();
 * bool param_4 = obj.empty();
 */