There are 16 pieces of black and white chess pieces of the same size in a box. If there must be 2 chess pieces of the same color, the minimum number of chess pieces must be drawn.
一个盒子里有黑、白两种大小相同的棋子各16枚，要想使摸出的棋子一定有2枚同色的，最少要摸出多少枚棋子．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<result>3</result>