Again, Akko breaks a wall in little witch academia when she's practicing how to fly on broom! She doesn't want Diana to know about this, as Diana may be mad at her, so she turns to Ursula Sensei for help.

Ursula Sensei gives Akko two kinds of bricks:

• width , height
• width , height

Akko can use these two kinds of brick for INFINITE times, and she CANNOT ROTATE the brick.

Now Akko must use these two kinds of bricks to fill the wall with width and height . And in order to make the wall more stable, Akko hopes that between any two adjacent layers, there can be no BRICK GAP up and down except the left and right side.

A legal situation is like this:

And an illegal situation is like this:

as you can see, there's a BRICK GAP in an illegal situation:

Specially, you can fill the wall with only one kind of brick, which means the following situation is legal:

Now Akko wants to know how many different legal situations there are. Two situations are different if and only if in some layer, they have different brick orders.