5 empty bottles can be exchanged for 1 bottle of soda. A classmate drank 161 bottles of soda, some of which were exchanged with empty bottles. Then how many bottles of soda should he buy at least?
用5个空瓶可以换1瓶汽水，某班同学喝了161瓶汽水，其中有一些是用空瓶换的，那么他至少要买多少瓶汽水．
<result>135</result>