What is the result of calculating 89-88+87-86+...+5-4+3-2+1?
计算89-88+87-86+…+5-4+3-2+1的结果是多少．
<gadget id="calculator">89 - 1</gadget>
<output>88</output>

<gadget id="calculator">88 / 2</gadget>
<output>44</output>

<gadget id="calculator">44 * 1</gadget>
<output>44</output>

<gadget id="calculator">44 + 1</gadget>
<output>45</output>

<result>45</result>