Students in Class 6 (2) of Xinxing Primary School voted for two monitors (one monitor and one deputy monitor) from 5 candidates, and it was stipulated that each student must choose two monitors from these 5 candidates. If it is to be guaranteed that no less than 5 students must have voted for the same two candidates, how many people should at least participate in the voting?
新兴小学六(二)班同学从5名候选人中投票选举两位班长(一位正班长，一位副班长)，规定每位同学必须从这5人中任选两人．如果要保证必有不少于5个同学投了相同两位候选人的票，那么参加投票选举的人数至少应有多少人？
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<gadget id="calculator">80 + 1</gadget>
<output>81</output>

<result>81</result>