From 1 to 100, how many zeros are there at the end?
从1乘到100，末尾一共有多少个0．
<gadget id="calculator">100 / 5</gadget>
<output>20</output>

<gadget id="calculator">100 / 25</gadget>
<output>4</output>

<gadget id="calculator">20 + 4</gadget>
<output>24</output>

<result>24</result>