| p_1  | p_2  | p_3  | p_4  |
---------------------------------
 v_1 | s_1  | s_2  | s_3  | s_4  |
 v_2 | s_5  | s_6  | s_7  | s_8  |
 v_3 |      | s_9  |      | s_10 |
 v_4 | s_11 | s_12 |      | s_13 |
 v_5 |      |      | s_14 |      |