Divide 1, 2, 3, 4, 5, and 6 into three groups, and how many ways are there in which exactly one group sums to 7?
将1，2，3，4，5，6分成三组，其中恰有一组和为7的分法共有多少种．
<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<result>6</result>