How many different ways are there to put 5 identical shuttlecocks in three different boxes A, B, and C? (empty boxes allowed)
把5个相同的羽毛球放人甲、乙、丙三个不同的盒子内，有多少种不同的放法．(允许有空盒子)
<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">3 + 12 + 6</gadget>
<output>21</output>

<result>21</result>