An airplane performs acrobatics, and its height after takeoff changes as follows (a positive number indicates the height of ascent): +9000 meters, -7200 meters, +5000 meters, -2300 meters. How much is the plane higher than the take-off point at this time?
一架飞机进行特技表演，起飞后的高度变化如下(正数表示上升的高度)：+9000米，-7200米，+5000米，-2300米．此时飞机比起飞点高多少米？
<gadget id="calculator">9_000 - 7_200</gadget>
<output>1_800</output>

<gadget id="calculator">5_000 - 2_300</gadget>
<output>2_700</output>

<gadget id="calculator">1_800 + 2_700</gadget>
<output>4_500</output>

<result>4_500</result>