There are 6 balls of red, yellow, and white in the box. If you want to get the balls, there must be 2 balls of the same color, at least how many balls you need to get.
盒子里面有红、黄、白三种颜色的球各6个，要想摸出的球一定有2个同色，至少要摸出多少个球．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>