13. Given that the area of quadrilateral $A B C D$ is $2021, E$ is a point on $A D$, and the centroids of $\triangle B C E, \triangle A B E$, $\triangle C D E$ are $G_{1}, G_{2}, G_{3}$, respectively, then the area of $\triangle G_{1} G_{2} G_{3}$ is $\qquad$
Answer: $\frac{2021}{9}$