Divide the eight numbers 12, 13, 14, 15, 16, 17, 18, and 19 into two groups (four numbers in each group), so that the sum of the two groups of numbers is equal; then how many such grouping methods are there?
将12、13、14、15、16、17、18、19这八个数分成两组(每组四个数)，使两组数的和相等；那么这样的分组方法有多少种．
<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<result>4</result>