A and B set off at the same time from point A of the road around the lake with a circumference of 4,000 meters. After 30 minutes, they meet for the third time. It is known that A travels 20 meters more per minute than B per minute. Then, what is the shortest distance along the highway from the point A where the two meet for the third time?
甲、乙两人从周长为4000米的环湖公路的一点A，背向同时出发，30分钟后，两人第三次相遇．已知甲每分钟比乙每分钟多行20米，那么，两人第三次相遇的地点，与A点沿公路的最短距离是多少米？
<gadget id="calculator">4_000 * 3</gadget>
<output>12_000</output>

<gadget id="calculator">20 * 30</gadget>
<output>600</output>

<gadget id="calculator">12_000 - 600</gadget>
<output>11_400</output>

<gadget id="calculator">11_400 / 2</gadget>
<output>5_700</output>

<gadget id="calculator">5_700 - 4_000</gadget>
<output>1_700</output>

<result>1_700</result>