
I would like you to implement a module named TopModule with the following
interface. All input and output ports are one bit unless otherwise
specified.

 - input  A (2 bits)
 - input  B (2 bits)
 - output z

The module should implement a circuit that has two 2-bit inputs A[1:0]
and B[1:0], and produces an output z. The value of z should be 1 if A =
B, otherwise z should be 0.

