There are 20 male and female students in a class, at least how many people should be selected to ensure that there are boys and girls among the selected people.
某班男女生各20人，至少选取多少人才能保证选出的人中有男生、女生．
<gadget id="calculator">20 + 1</gadget>
<output>21</output>

<result>21</result>