Xiao Ming's home is 306 meters away from the school. He goes to and from school twice a day. How many meters did he walk in total?
小明家离学校有306米，他每天往返学校两次，一共走多少米？
<gadget id="calculator">306 * 4</gadget>
<output>1_224</output>

<result>1_224</result>