
Consider the function f shown in the Karnaugh map below. d is don't-care,
which means you may choose to output whatever value is convenient.
Implement this function.

                x[1]x[2]
  x[3]x[4]   00  01  11  10
        00 | d | 0 | d | d |
        01 | 0 | d | 1 | 0 |
        11 | 1 | 1 | d | d |
        10 | 1 | 1 | 0 | d |

module TopModule (
  input [4:1] x,
  output logic f
);

