There are several hats in a box, all but 2 are red, all but 2 are blue, and all but 2 are yellow, how many hats are there in the box?
一个箱子里放着几顶帽子，除2顶以外都是红的，除2顶以外都是蓝的，除2顶以外都是黄色的，箱子中一共有多少顶帽子．
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<result>3</result>