A store promotes the activity of exchanging empty bottles for soda, and stipulates that every 3 empty bottles can be exchanged for a bottle of soda. Teacher Zhang bought 10 bottles of soda for the basketball team students, so how many students can drink soda (the rule is that each person drinks 1 bottle).
某商店推行空瓶兑换汽水活动，规定每3个空瓶子可以换一瓶汽水，体育张老师买了10瓶汽水供篮球队的同学，那么共有多少个同学可以喝上汽水(规定每人喝一瓶)．
<gadget id="calculator">10 + 3 + 1 + 1</gadget>
<output>15</output>

<result>15</result>