T | f1 | f2 | f3 | d |
r1 | 0 | 1 | 0 | {1} |
r2 | 2 | 1 | 0 | {1,2} |
r3 | 1 | 0 | 2 | {1,3} |
r4 | 0 | 0 | 1 | {2} |