20
00 -> A
01 -> B
10 -> C
11 -> D
6566 -> Z
6567 -> Z
6568 -> Z
6665 -> Z
6667 -> Z
6668 -> Z
6765 -> Z
6766 -> Z
6768 -> Z
6865 -> Z
6866 -> Z
6867 -> Z
A -> _
B -> _
C -> _
D -> _