20. Fill the squares in Figure 1 with the shapes in Figure 2 (each type of shape can be used multiple times, and black squares must be avoided). Two identical shapes cannot be adjacent (shapes that share a side are considered adjacent, while shapes that only share a vertex are not adjacent). Each type of shape can be rotated or flipped before being placed in the grid. Each type of shape is represented by a letter, and the letters in the small squares indicate which type of shape fills that square. In the left figure, three rows are marked with arrows. Suppose the first marked row uses $\mathbf{A}$ shapes, the second marked row uses $\mathbf{B}$ shapes, and the third marked row uses $\mathbf{C}$ shapes, then $\overline{A B C}=$ $\qquad$ For example, if we fill as shown in Figure 3 (please ignore the last two rows, which are just for illustration to explain the meaning of $\mathrm{A}$, $\mathrm{B}$, and $\mathbf{C}$), the first marked row uses 2 shapes (one horizontal $\mathbf{I}$ shape and one rotated and flipped $L$ shape), so $A=2$; the second marked row uses 4 shapes (one flipped $Z$ shape, one rotated $\mathbf{T}$ shape, one $\mathbf{T}$ shape, and one $O$ shape), so $B=4$; the third marked row uses 4 shapes, so $C=4$. Therefore, the answer is 244.
【Answer】 333 So $\overline{A B C}=333$.