Divide the eight numbers 1, 2, 3, 4, 5, 6, 7, and 8 into two groups on average, so that the sum of the four numbers in each group is equal. How many ways are there?
把1、2、3、4、5、6、7、8这八个数平均分成两组，使每组四个数相加的和相等，这样的分法有多少种．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>