import java.util.Stack; public class Solution { Stack<Integer> stack1 = new Stack<Integer>(); Stack<Integer> stack2 = new Stack<Integer>(); public void push(int node) { Integer data; while(stack2.size()!=0) { stack1.push(stack2.pop()); } stack2.push(node); while(stack1.size()!=0) { stack2.push(stack1.pop()); } } public int pop() { if(stack2.size()!=0) { return stack2.pop(); } return 0; } }