MAYBE
* Step 1: Failure MAYBE
  + Considered Problem:
      - Strict TRS:
          a__U11(X1,X2) -> U11(X1,X2)
          a__U11(tt(),L) -> a__U12(tt(),L)
          a__U12(X1,X2) -> U12(X1,X2)
          a__U12(tt(),L) -> s(a__length(mark(L)))
          a__length(X) -> length(X)
          a__length(cons(N,L)) -> a__U11(tt(),L)
          a__length(nil()) -> 0()
          a__zeros() -> cons(0(),zeros())
          a__zeros() -> zeros()
          mark(0()) -> 0()
          mark(U11(X1,X2)) -> a__U11(mark(X1),X2)
          mark(U12(X1,X2)) -> a__U12(mark(X1),X2)
          mark(cons(X1,X2)) -> cons(mark(X1),X2)
          mark(length(X)) -> a__length(mark(X))
          mark(nil()) -> nil()
          mark(s(X)) -> s(mark(X))
          mark(tt()) -> tt()
          mark(zeros()) -> a__zeros()
      - Signature:
          {a__U11/2,a__U12/2,a__length/1,a__zeros/0,mark/1} / {0/0,U11/2,U12/2,cons/2,length/1,nil/0,s/1,tt/0,zeros/0}
      - Obligation:
          innermost runtime complexity wrt. defined symbols {a__U11,a__U12,a__length,a__zeros
          ,mark} and constructors {0,U11,U12,cons,length,nil,s,tt,zeros}
  + Applied Processor:
      NaturalPI {shape = Mixed 3, restrict = NoRestrict, uargs = UArgs, urules = URules, selector = Nothing}
  + Details:
      Incompatible
MAYBE