$8$
22. (5 points)
In the Even-Even Kingdom, people hate odd numbers so much that they don't even want to see any odd digits. Therefore, when communicating, they replace odd digits with symbols. For example, when writing “$3 \times 4=12$”, they would write “$\rightsquigarrow \times 4=\uparrow 2$”.

The Even-Even Kingdom represents a one-digit by three-digit multiplication problem in a horizontal format. In this problem (including the two factors and the final product), the maximum number of squares that can be used is $\qquad$.