class Solution

{

public:

    void push(int node) {

        stack1.push(node);

    }

    int pop() {

        if(stack2.empty())

        {

            while(!stack1.empty())

            {

                int num = stack1.top();

                stack2.push(num);

                stack1.pop();

            }

        }

        int res = stack2.top();

        stack2.pop();

        return res;

    }

private:

    stack<int> stack1;

    stack<int> stack2;

};