#ignore + -
#axiom
C(5,5)AA++AA-AAAAD(0)
#rules
C(a,b) > A : b<5 -> C(a,b+1)
C(a,b) > A : b>=5 ; a>0 -> C(a-1,0)
C(a,b) < A : b>=5 ; a>0 -> B
B<D(a) -> D(a+1)
B<A -> B
B -> A