13. (5 points) As shown in the grid diagram, the image of monkey $K I N G$ is composed of several arcs and line segments, where the radius of the largest circle is 4, then the area of the shaded part is $\qquad$ .【Take pi as 3】
【Solution】Since the radius of the largest circle is 4, the side length of each square is $4 \div 8=0.5$
$$
\begin{array}{l}
3 \times 4^{2}-3 \times(0.5 \times 4)^{2}-(0.5 \times 4) \times(0.5 \times 2)-3 \times 0.5^{2} \times 2 \\
=3 \times 16-3 \times 4-2 \times 1-3 \times 0.25 \times 2 \\
=48-12-2-1.5 \\
=32.5
\end{array}
$$

Answer: The area of the shaded part in the figure is 32.5.
Therefore, the answer is: 32.5.