Calculate how much 2015+638-1015+492+2015+362-1515+508=.
计算2015+638-1015+492+2015+362-1515+508=多少．
<gadget id="calculator">638 - 1_015</gadget>
<output>-377</output>

<gadget id="calculator">362 - 1_515</gadget>
<output>-1_153</output>

<gadget id="calculator">2_015 + (-377) + 492 + 2_015 + (-1_153) + 508</gadget>
<output>3_500</output>

<result>3_500</result>