A and B are exercising on a circular track. They start from both ends of a certain diameter of the track at the same time and walk toward each other. When B walks 100 meters, they meet for the first time. After meeting, the two continue to move forward, and meet for the second time at 60 meters before A completes a week. Find the circumference of this circular runway.
甲、乙两人在一条圆形跑道上锻炼，他们分别从跑道某条直径的两端同时出发，相向而行，当乙走了100米时，他们第一次相遇．相遇后两人继续前进，在甲走完一周前60米处第二次相遇，求这条圆形跑道的周长．
<gadget id="calculator">100 * 3</gadget>
<output>300</output>

<gadget id="calculator">300 - 60</gadget>
<output>240</output>

<gadget id="calculator">240 * 2</gadget>
<output>480</output>

<result>480</result>