Some students plant a batch of trees. If each person plants 4 trees, there are still 20 trees left in total; if each person plants 8 trees, there will be one person who neither needs to plant 8 trees, nor will he not plant 1 tree. How many students are there in total?
有几个学生种一批树．如果每人种4棵，总数还剩下20棵；如果每人种8棵，就有一个人既不用种8棵，也不会1棵也没种．一共有学生多少人．
<gadget id="calculator">8 - 4</gadget>
<output>4</output>

<gadget id="calculator">24 / 4</gadget>
<output>6</output>

<result>6</result>