在谷歌地图中拖动标记并更改与其对应的坐标

If i have two markers on google maps and i reserve the longitude and latitude of the first marker in variables (fromLan, fromLat) and longitude and latitude of the second marker in variables (toLan, toLat). I want when dragging one of them to change the longitude and latitude of this marker in order to know whether to change the (fromLan, fromLat) variables or the (toLan, toLat) variables . If i have two markers on google maps and i rese