Two people, A and B, set off from A and B at the same time and walk toward each other. The first meeting is 300 meters away from A. Continue to move forward after meeting, turn back after arriving at the destination, and meet for the second time at 100 meters away from B. Question: What is the distance between A and B?
甲、乙两人从A、B两地同时出发，相向而行，第一次相遇在距A地300米处．相遇后继续前进，到达目的地后又折回，第二次相遇在距B地100米处．问：A、B两地间的距离．
<gadget id="calculator">300 * 3</gadget>
<output>900</output>

<gadget id="calculator">900 - 100</gadget>
<output>800</output>

<result>800</result>