Mom bought some apples, ate half of them on the first day, and the remaining half on the second day. At this time, there were 4 apples left. How many apples did my mother buy?
妈妈买了一些苹果，第一天吃了一半，第二天吃了剩下的一半，这时剩下4个，妈妈买了多少个苹果？
<gadget id="calculator">4 * 2 * 2</gadget>
<output>16</output>

<result>16</result>