345678每条线上的三个数的和15

简介：Unlike the first line of defense, which relied on the mountains, the second line of defense relied on the water flow of the canal. However, once the invaders entered the fort, the defenders at various places must immediately seize all the ships on the canal and move them to the four cities. The city and sixteen bastions served as strongholds, as well as the riverbank defense on the west side of the canal, making it impossible for the Jianlu to cross the canal easily.