There are 3 red, yellow, blue and white table tennis balls of the same size in the box. If you want to get 2 balls of the same color, how many balls should you get at least.
盒子里有同样大小的红、黄、蓝、白四种颜色的乒乓球各3个，要想摸出的球有2个同色的，最少要摸出多少个球．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<result>5</result>