and B are moving towards each other at a constant speed along the rectangular road ABCD. At the beginning, A is at A and B is at C. They start at the same time. When they meet for the first time, A walks 50 meters. When they meet for the second time, B walks another 20 meters and returns to C. What is the circumference of this road in meters?
甲、乙两人沿长方形道路ABCD匀速相对而行，开始时甲在A处，乙在C处，同时出发．第一次相遇时甲走了50米，第二次相遇时，乙再走20米就回到C处，这条道路的周长是多少米．
<gadget id="calculator">50 * 3</gadget>
<output>150</output>

<gadget id="calculator">150 - 20</gadget>
<output>130</output>

<gadget id="calculator">130 * 2</gadget>
<output>260</output>

<result>260</result>