1. As shown in the right figure, the surroundings of a square pond with a side length of 12 meters are grasslands. There are wooden stakes at points $A, B, C, D$ on the pond's edge, and $A B=B C=C D=3$ meters. Now, a 4-meter-long rope is used to tie a sheep to one of these wooden stakes. To maximize the area where the sheep can graze on the grass, the rope should be tied to the stake at $\qquad$.