| in  | sel  |  a  |  b  |  c  |  d  |
|  0  |  00  |  0  |  0  |  0  |  0  |
|  0  |  01  |  0  |  0  |  0  |  0  |
|  0  |  10  |  0  |  0  |  0  |  0  |
|  0  |  11  |  0  |  0  |  0  |  0  |
|  1  |  00  |  1  |  0  |  0  |  0  |
|  1  |  01  |  0  |  1  |  0  |  0  |
|  1  |  10  |  0  |  0  |  1  |  0  |
|  1  |  11  |  0  |  0  |  0  |  1  |