A large embankment was built around a lake, and a willow tree was planted every 4 meters on the embankment, and two peach trees were planted between two adjacent willow trees. A total of 400 peach trees were planted on the embankment. How many meters is this embankment long?
在一个湖泊周围筑了一条大堤，堤上每隔4米栽柳树一棵，然后在相邻两棵柳树之间栽2棵桃树，堤上一共栽了桃树400棵．这条大堤长多少米．
<gadget id="calculator">400 / 2</gadget>
<output>200</output>

<gadget id="calculator">200 * 4</gadget>
<output>800</output>

<result>800</result>