Two people, A and B, start from A and B respectively and walk towards each other. After arriving at the destination, they immediately turn around and return to the starting point. The distance between them is 800 meters from A for the first time, and 500 meters away from B for the second time. , How many meters is the distance between B and B?
甲、乙二人分别从A，B两地出发相向而行，到达目的地后马上掉头回到出发地，他们第一次相遇距A地800米，第二次相遇距B地500米，A，B两地相距多少米？
<gadget id="calculator">800 * 3</gadget>
<output>2_400</output>

<gadget id="calculator">2_400 - 500</gadget>
<output>1_900</output>

<result>1_900</result>