20
0S -> S0
1S -> S1
C0 -> 0C
C1 -> 1C
0C -> D
1C -> E
S1 -> BSC
S0 -> ASC
0 -> S0
1 -> S0
FA -> AF
FB -> BF
GA -> AG
GB -> BG
AS -> SA
BS -> SB
SA -> F
SB -> G
FD -> _
GE -> _