Once upon a time, there was an old man called YuGong live near two mountains which let him took a long time to walk to the other side, so he wanted to move them_
He told his family that he must move it and his family also need to help him to move the mountains to the sea.
The next day, there was another old man, he saw YuGong moving the mountains and said that YuGong could never move them because he was old and weak.