Implement a queue with two stacks.

The declaration of the queue is as follows , Please implement its two functions appendTail and deleteHead , The functions of inserting integers at the end of the queue and deleting integers at the head of the queue are respectively completed .( If there are no elements in the queue ,deleteHead  Operation return -1 )

 Input ：
["CQueue","appendTail","deleteHead","deleteHead"]
[[],[3],[],[]]
 Output ：[null,null,3,-1]

 Input ：
["CQueue","deleteHead","appendTail","appendTail","deleteHead","deleteHead"]
[[],[],[5],[2],[],[]]
 Output ：[null,-1,null,null,5,2]

class CQueue {
private: 
    stack<int> instack;
    stack<int> outstack;/* An input stack , One as an output stack */
public:
    CQueue() {

    }
    
    void appendTail(int value) {
        instack.push(value);
    }
    
    int deleteHead() {
        if(!outstack.empty()){
            int value = outstack.top();
            outstack.pop();
            return value;
        }
        else{
            while(!instack.empty()){
                int top = instack.top();
                instack.pop();
                outstack.push(top);
            }
            if(outstack.empty()){
                return -1;
            }else{
                int output = outstack.top();
                outstack.pop();
                return output;
            }
        }
    }
};

/**
 * Your CQueue object will be instantiated and called as such:
 * CQueue* obj = new CQueue();
 * obj->appendTail(value);
 * int param_2 = obj->deleteHead();
 */