MAYBE
* Step 1: Failure MAYBE
  + Considered Problem:
      - Strict TRS:
          a__U11(X1,X2) -> U11(X1,X2)
          a__U11(tt(),L) -> s(a__length(mark(L)))
          a__and(X1,X2) -> and(X1,X2)
          a__and(tt(),X) -> mark(X)
          a__isNat(X) -> isNat(X)
          a__isNat(0()) -> tt()
          a__isNat(length(V1)) -> a__isNatList(V1)
          a__isNat(s(V1)) -> a__isNat(V1)
          a__isNatIList(V) -> a__isNatList(V)
          a__isNatIList(X) -> isNatIList(X)
          a__isNatIList(cons(V1,V2)) -> a__and(a__isNat(V1),isNatIList(V2))
          a__isNatIList(zeros()) -> tt()
          a__isNatList(X) -> isNatList(X)
          a__isNatList(cons(V1,V2)) -> a__and(a__isNat(V1),isNatList(V2))
          a__isNatList(nil()) -> tt()
          a__length(X) -> length(X)
          a__length(cons(N,L)) -> a__U11(a__and(a__isNatList(L),isNat(N)),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(and(X1,X2)) -> a__and(mark(X1),X2)
          mark(cons(X1,X2)) -> cons(mark(X1),X2)
          mark(isNat(X)) -> a__isNat(X)
          mark(isNatIList(X)) -> a__isNatIList(X)
          mark(isNatList(X)) -> a__isNatList(X)
          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__and/2,a__isNat/1,a__isNatIList/1,a__isNatList/1,a__length/1,a__zeros/0,mark/1} / {0/0,U11/2
          ,and/2,cons/2,isNat/1,isNatIList/1,isNatList/1,length/1,nil/0,s/1,tt/0,zeros/0}
      - Obligation:
          innermost runtime complexity wrt. defined symbols {a__U11,a__and,a__isNat,a__isNatIList,a__isNatList
          ,a__length,a__zeros,mark} and constructors {0,U11,and,cons,isNat,isNatIList,isNatList,length,nil,s,tt,zeros}
  + Applied Processor:
      NaturalPI {shape = Mixed 3, restrict = NoRestrict, uargs = UArgs, urules = URules, selector = Nothing}
  + Details:
      Incompatible
MAYBE