+-------+-------+-------+
| _ 2 _ | _ _ _ | _ _ _ |
| _ _ _ | 6 _ _ | _ _ 3 |
| _ 7 4 | _ 8 _ | _ _ _ |
+-------+-------+-------+
| _ _ _ | _ _ 3 | _ _ 2 |
| _ 8 _ | _ 4 _ | _ 1 _ |
| 6 _ _ | 5 _ _ | _ _ _ |
+-------+-------+-------+
| _ _ _ | _ 1 _ | 7 8 _ |
| 5 _ _ | _ _ 9 | _ _ _ |
| _ _ _ | _ _ _ | _ 4 _ |
+-------+-------+-------+
