A total of 52 teachers and students went out for a spring outing. When they arrived, the class teacher wanted to buy each of them a bottle of mineral water, and gave the monitor the money for the mineral water. After the squad leader arrived at the store, he found that the store was conducting a promotional activity, stipulating that every 5 empty bottles could be exchanged for 1 bottle of mineral water. As long as the squad leader buys as many bottles of mineral water as possible, he can guarantee one bottle for each person.
师生共52人外出春游，到达后，班主任要给每人买一瓶矿泉水，给了班长买矿泉水的钱．班长到商店后，发现商店正在进行促销活动，规定每5个空瓶可换1瓶矿泉水．班长只要买多少瓶矿泉水，就可以保证每人一瓶．
<gadget id="calculator">4 * 10</gadget>
<output>40</output>

<gadget id="calculator">40 + 2</gadget>
<output>42</output>

<result>42</result>