Mineral water is one yuan per bottle. In order to recycle empty bottles, the store can exchange 5 empty mineral water bottles for one bottle of mineral water. A group of children have a total of 20 yuan. How many bottles of mineral water can they drink at most?
矿泉水每瓶一元，店家为了回收空瓶，在他那里用5个空矿泉水瓶可换一瓶矿泉水．一群小朋友共有20元钱，他们最多可以喝多少瓶矿泉水．
<gadget id="calculator">20 / 1</gadget>
<output>20</output>

<gadget id="calculator">20 / 1 / 5</gadget>
<output>4</output>

<gadget id="calculator">20 + 4 + 1</gadget>
<output>25</output>

<result>25</result>