The stadium is the starting point of buses No. 1 and No. 13. Bus No. 1 departs every 3 minutes, and Bus No. 13 departs every 5 minutes. After the two cars depart at the same time, how many minutes later will they depart at the same time?
体育场是1路和13路汽车的起点站．1路汽车每3分钟发车一次，13路汽车每5分钟发车一次．这两路汽车同时发车以后，至少再过多少分钟后又同时发车？
<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<result>15</result>