There are 5 red, yellow, and black balls in the box. If you want to draw balls of all three colors, at least how many balls must be drawn.
盒子里有红、黄、黑三种颜色的球各5个，要使摸出球的三种颜色都有，至少要摸出多少个．
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">10 + 1</gadget>
<output>11</output>

<result>11</result>