There are 10 red balls and 10 yellow balls in the bag, at least how many balls must be touched to ensure that there are red balls and yellow balls.
袋子里有10个红球和10个黄球，至少要摸多少个球才能保证有红球和黄球．
<gadget id="calculator">10 + 1</gadget>
<output>11</output>

<result>11</result>