(1+4+7+10+...+40)-(4+7+10+13+...+37)=how much.
(1+4+7+10+…+40)-(4+7+10+13+…+37)=多少．
<gadget id="calculator">37 - 37</gadget>
<output>0</output>

<gadget id="calculator">39 + 40</gadget>
<output>79</output>

<gadget id="calculator">1 + 0 + 79</gadget>
<output>80</output>

<result>80</result>