A certain unit of the People's Liberation Army was going to the border. It was originally planned to march for 18 days. The actual average was 12 kilometers more than the original plan every day. It turned out to arrive 3 days earlier. How many kilometers did it march this time?
解放军某部开往边境，原计划需要行军18天，实际平均每天比原计划多行12千米，结果提前3天到达，这次共行军多少千米？
<gadget id="calculator">18 - 3</gadget>
<output>15</output>

<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<gadget id="calculator">12 * 5 * 18</gadget>
<output>1_080</output>

<result>1_080</result>