Luokittelija

input/code.cpp:1:1: error: expected unqualified-id before numeric constant
 20
 ^~

20
00 -> A
01 -> B
10 -> C
11 -> D
AB -> Z
AC -> Z
AD -> Z
BA -> Z
BC -> Z
BD -> Z
CA -> Z
CB -> Z
CD -> Z
DA -> Z
DB -> Z
DC -> Z
A -> _
B -> _
C -> _
D -> _