30 students go out for an outing and plan to drink a bottle of soda each. The store stipulates that every 5 empty bottles can be exchanged for a bottle of soda. So at least how many bottles of soda will they buy.
30个同学出去郊游，计划每人喝一瓶汽水，商店规定：每5个空瓶可以换回一瓶汽水．那么他们至少要买多少瓶汽水．
<result>24</result>