The customer bought a 15-yuan item from the salesperson and paid a 50-yuan bill. The salesperson had no change, so he exchanged the change at the adjacent counter. After the delivery is completed and the customer leaves, the neighboring cabinet finds that the 50 yuan bill is a counterfeit currency, and the salesperson returns another 50 yuan to the neighboring cabinet. Then, how much is the salesperson’s loss?
顾客向售货员购买15元的物品，付了一张面值50元的钞票，售货员没有零钱找，便向相邻柜台兑换了零钱．当交割完毕顾客走后，邻柜发现这张50元钞票是假币，该售货员于是又还给邻柜50元钱，那么，该售货员遭受了多少元的损失．
<gadget id="calculator">15 + 35</gadget>
<output>50</output>

<result>50</result>