Add 4 to a certain number, multiply by 4, subtract 4, and divide by 4. The result is still 4. What is the number?
某数加上4，乘以4，减去4，再除以4，其结果还是4，这个数是多少．
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">16 + 4</gadget>
<output>20</output>

<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">5 - 4</gadget>
<output>1</output>

<result>1</result>