The highest floor above the ground of a building is recorded as +18 floors, and the lowest floor below the ground is recorded as -5 floors. How many floors does this building have?
一幢大楼地面以上最高层记录为+18层，地面以下最底层记为-5层，这幢大楼共有多少层．
<gadget id="calculator">5 + 18</gadget>
<output>23</output>

<result>23</result>