| Banned Users in Server |
|1) U1      ->  Id1      |
|2) U2      ->  Id2      |
|3) U3      ->  Id3      | 
|4) U4      ->  Id4      |
|5) U5      ->  Id5      |
--------------------------
|     ←       |      →   |
| 1 | 2 |  3  |  4  |  5  |