private Stack<Integer> stack1;
    private Stack<Integer> stack2;

    public Queue() {
       stack1 = new Stack<Integer>();
       stack2 = new Stack<Integer>();
    }

    public void push(int element) {
        stack1.push(element);
    }

    public int pop() {
        if(!stack2.isEmpty()){
            return stack2.pop();
        } else{
            while(!stack1.isEmpty()){
                stack2.push(stack1.pop());
            }
        }
        return stack2.pop();
    }

    public int top() {
        if(!stack2.isEmpty()){
            return stack2.peek();
        } else{
            while(!stack1.isEmpty()){
                stack2.push(stack1.pop());
            }
        }
        return stack2.peek();
    }