The sum of six consecutive natural numbers is 129, what is the sum of the last three numbers?
连续六个自然数的和是129，那么后三个数的和是多少．
<gadget id="calculator">19 + 3</gadget>
<output>22</output>

<gadget id="calculator">19 + 4</gadget>
<output>23</output>

<gadget id="calculator">19 + 5</gadget>
<output>24</output>

<gadget id="calculator">22 + 23 + 24</gadget>
<output>69</output>

<result>69</result>