4 empty bottles can be exchanged for one bottle of soda. A class of students drank a total of 112 bottles of soda during an activity, and some of them were exchanged for the remaining empty bottles. Then how many bottles of soda should they buy at least?
4个空瓶可以换一瓶汽水，某班同学在一次活动期间，共喝了112瓶汽水，其中有一些是用喝剩下的空瓶换的，那么他们至少要买多少瓶汽水．
<gadget id="calculator">112 / 4</gadget>
<output>28</output>

<gadget id="calculator">28 * 3</gadget>
<output>84</output>

<result>84</result>