The library, the swimming pool, and the children's palace stand on a straight road, and the distance from the swimming pool to the library and the children's palace are equal. Xiao Ming and Xiao Hua set off from the library and the Children's Palace at the same time and walked towards each other. Xiao Ming met Xiao Hua after passing 100 meters from the swimming pool station. Then the two moved on. After Xiaoming arrived at the Children's Palace Station, he immediately returned along the original road, and after passing the Swimming Hall Station, he caught up with Xiaohua 300 meters away. How many meters are there between the library and the Children's Palace?
图书馆，游泳馆，少年宫三个站在一条笔直的公路上，且游泳馆到图书馆，少年宫两站的距离相等．小明和小华分别从图书馆，少年宫两站同时出发相向而行．小明超过游泳馆站100米后与小华相遇．然后二人继续前进．小明到达少年宫站后立即沿原路返回，经过游泳馆站后300米追上小华．则图书馆，少年宫两站相距多少米．
<gadget id="calculator">400 / 2</gadget>
<output>200</output>

<gadget id="calculator">200 + 100</gadget>
<output>300</output>

<gadget id="calculator">300 * 2</gadget>
<output>600</output>

<result>600</result>