P1 | S1 | S2 | S3 | S4 |
S1 | 1 | 1/2 | 1/3 | 1/2 |
S2 | 2 | 1 | 1/3 | 1/2 |
S3 | 3 | 3 | 1 | 2 |
S4 | 2 | 2 | 1/2 | 1 |