class Solution
{
public:
    void push(int node) {
        stack1.push(node);
    }

    int pop() {
        if (stack2.empty()){
            while (!stack1.empty()){
                int shu = stack1.top();
                stack1.pop();
                stack2.push(shu);
            }
        }
        int jieguo;
        jieguo = stack2.top();
        stack2.pop();
        return jieguo;
    }

private:
    stack<int> stack1;
    stack<int> stack2;
};