class MaxQueue {

    Queue<Integer> queue;
    Deque<Integer> deque;

    public MaxQueue() {
        queue = new LinkedList<>();
        deque = new LinkedList<>();
    }
    
    public int max_value() {
        return deque.isEmpty() ? -1 : deque.peekFirst();
    }
    
    public void push_back(int value) {
        queue.offer(value);
        while(!deque.isEmpty()&&deque.peekLast() < value){
            deque.pollLast();
        }
        deque.offerLast(value);
    }
    
    public int pop_front() {
        if(queue.isEmpty()) return -1;
        if(queue.peek().equals(deque.peekFirst())){
            //如果递减队列首元素相同，删除
            deque.pollFirst();
        }
        return queue.poll();
    }
}

/**
 * Your MaxQueue object will be instantiated and called as such:
 * MaxQueue obj = new MaxQueue();
 * int param_1 = obj.max_value();
 * obj.push_back(value);
 * int param_3 = obj.pop_front();
 */