In the fifth grade, there are two classes of students participating in the activity, 8 people make up a group with 7 people, and 9 people make up a group with 8 people, at least how many people participate in the activity.
五年级有两个班同学参加活动，8个人编一个组余7人，9个人编一个组余8人，参加活动至少有多少人．
<gadget id="calculator">72 - 1</gadget>
<output>71</output>

<result>71</result>