Calculation: 1+3-2+2+4-3+3+5-4+4+6-5+...+36+38-37=how much.
计算：1+3-2+2+4-3+3+5-4+4+6-5+…+36+38-37=多少．
<gadget id="calculator">1 + 38</gadget>
<output>39</output>

<gadget id="calculator">38 / 2</gadget>
<output>19</output>

<gadget id="calculator">39 * 19</gadget>
<output>741</output>

<gadget id="calculator">741 - 39</gadget>
<output>702</output>

<result>702</result>