The average of 4 numbers is 555, two of which are 666 and 888, what is the average of the other two numbers.
4个数的平均数是555，其中两个数是666和888，其余两个数的平均数是多少．
<gadget id="calculator">555 * 4</gadget>
<output>2_220</output>

<gadget id="calculator">2_220 - 666 - 888</gadget>
<output>666</output>

<gadget id="calculator">666 / 2</gadget>
<output>333</output>

<result>333</result>