Among the students participating in the four interest groups of gymnastics, martial arts, piano, and calligraphy, each student can participate in two interest groups at most. In order to ensure that there are no less than 6 students with exactly the same situation in the selected interest group, the number of students participating in the group should be at least how many.
参加体操、武术、钢琴、书法四个兴趣小组的学生中，每人最多可以参加两个兴趣小组．为了保证所选兴趣小组的情况完全相同的学生不少于6人，则参加小组的学生至少有多少人．
<gadget id="calculator">6 * 5</gadget>
<output>30</output>

<gadget id="calculator">30 + 1</gadget>
<output>31</output>

<result>31</result>