A submarine is located at an altitude of -600 meters. It first floats up 100 meters and then submerges 300 meters. How many meters below the sea level is the submarine at this time?
一潜水艇所在的高度是-600米，先上浮100米，又潜入300米，这时潜水艇在海平面以下多少米．
<result>800</result>