There are two islands A and B in the lake. Both A and B have to swim back and forth between the two islands. The two set off from islands A and B at the same time. When they met for the first time, they were 700 meters away from island A, and when they met for the second time, they were 400 meters away from island B. Q: How far is the distance between the two islands?
湖中有A，B两岛，甲、乙二人都要在两岛间游一个来回．两人分别从A，B两岛同时出发，他们第一次相遇时距A岛700米，第二次相遇时距B岛400米．问：两岛相距多远？
<gadget id="calculator">700 * 3</gadget>
<output>2_100</output>

<gadget id="calculator">2_100 - 400</gadget>
<output>1_700</output>

<result>1_700</result>