There are 4 red balls and 4 blue balls of the same size in the box. It is required that there must be 2 balls of the same color, and at least how many balls must be drawn.
盒子里有同样大小的红色球和蓝色球各4个，要求摸出的球一定要有2个同色的，至少要摸出多少个球．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<result>3</result>