23 students from Class 6 and 3 participated in the dance and fencing interest groups, of which 17 participated in the dance interest group and 20 participated in the fencing interest group. How many people participated in both interest groups?
六3班同学有23人参加了舞蹈和击剑兴趣小组，其中参加舞蹈兴趣小组的有17人，参加击剑兴趣小组的有20人，两个兴趣小组都参加的有多少人．
<gadget id="calculator">20 - 23</gadget>
<output>-3</output>

<gadget id="calculator">17 + (-3)</gadget>
<output>14</output>

<result>14</result>