In order to recycle soda bottles, a store stipulates that 3 empty bottles can be exchanged for a bottle of soda. A man bought 10 bottles of soda, and after drinking them, he exchanged the empty bottles for soda, and asked him how many bottles of soda he could drink in total.
某商店为了回收汽水瓶，规定3个空瓶换一瓶汽水．一个人买了10瓶汽水，喝完之后，又拿空瓶去换汽水，问他一共可以喝到多少瓶汽水．
<gadget id="calculator">10 + 3 + 1 + 1</gadget>
<output>15</output>

<result>15</result>