* Step 1: Sum WORST_CASE(Omega(n^1),?)
    + Considered Problem:
        - Strict TRS:
            a__U11(X) -> U11(X)
            a__U11(tt()) -> tt()
            a__U21(X) -> U21(X)
            a__U21(tt()) -> tt()
            a__U31(X) -> U31(X)
            a__U31(tt()) -> tt()
            a__U41(X1,X2) -> U41(X1,X2)
            a__U41(tt(),V2) -> a__U42(a__isNatIList(V2))
            a__U42(X) -> U42(X)
            a__U42(tt()) -> tt()
            a__U51(X1,X2) -> U51(X1,X2)
            a__U51(tt(),V2) -> a__U52(a__isNatList(V2))
            a__U52(X) -> U52(X)
            a__U52(tt()) -> tt()
            a__U61(X1,X2,X3) -> U61(X1,X2,X3)
            a__U61(tt(),L,N) -> a__U62(a__isNat(N),L)
            a__U62(X1,X2) -> U62(X1,X2)
            a__U62(tt(),L) -> s(a__length(mark(L)))
            a__isNat(X) -> isNat(X)
            a__isNat(0()) -> tt()
            a__isNat(length(V1)) -> a__U11(a__isNatList(V1))
            a__isNat(s(V1)) -> a__U21(a__isNat(V1))
            a__isNatIList(V) -> a__U31(a__isNatList(V))
            a__isNatIList(X) -> isNatIList(X)
            a__isNatIList(cons(V1,V2)) -> a__U41(a__isNat(V1),V2)
            a__isNatIList(zeros()) -> tt()
            a__isNatList(X) -> isNatList(X)
            a__isNatList(cons(V1,V2)) -> a__U51(a__isNat(V1),V2)
            a__isNatList(nil()) -> tt()
            a__length(X) -> length(X)
            a__length(cons(N,L)) -> a__U61(a__isNatList(L),L,N)
            a__length(nil()) -> 0()
            a__zeros() -> cons(0(),zeros())
            a__zeros() -> zeros()
            mark(0()) -> 0()
            mark(U11(X)) -> a__U11(mark(X))
            mark(U21(X)) -> a__U21(mark(X))
            mark(U31(X)) -> a__U31(mark(X))
            mark(U41(X1,X2)) -> a__U41(mark(X1),X2)
            mark(U42(X)) -> a__U42(mark(X))
            mark(U51(X1,X2)) -> a__U51(mark(X1),X2)
            mark(U52(X)) -> a__U52(mark(X))
            mark(U61(X1,X2,X3)) -> a__U61(mark(X1),X2,X3)
            mark(U62(X1,X2)) -> a__U62(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__U11/1,a__U21/1,a__U31/1,a__U41/2,a__U42/1,a__U51/2,a__U52/1,a__U61/3,a__U62/2,a__isNat/1,a__isNatIList/1
            ,a__isNatList/1,a__length/1,a__zeros/0,mark/1} / {0/0,U11/1,U21/1,U31/1,U41/2,U42/1,U51/2,U52/1,U61/3,U62/2
            ,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__U21,a__U31,a__U41,a__U42,a__U51,a__U52,a__U61
            ,a__U62,a__isNat,a__isNatIList,a__isNatList,a__length,a__zeros,mark} and constructors {0,U11,U21,U31,U41,U42
            ,U51,U52,U61,U62,cons,isNat,isNatIList,isNatList,length,nil,s,tt,zeros}
    + Applied Processor:
        Sum {left = someStrategy, right = someStrategy}
    + Details:
        ()
* Step 2: DecreasingLoops WORST_CASE(Omega(n^1),?)
    + Considered Problem:
        - Strict TRS:
            a__U11(X) -> U11(X)
            a__U11(tt()) -> tt()
            a__U21(X) -> U21(X)
            a__U21(tt()) -> tt()
            a__U31(X) -> U31(X)
            a__U31(tt()) -> tt()
            a__U41(X1,X2) -> U41(X1,X2)
            a__U41(tt(),V2) -> a__U42(a__isNatIList(V2))
            a__U42(X) -> U42(X)
            a__U42(tt()) -> tt()
            a__U51(X1,X2) -> U51(X1,X2)
            a__U51(tt(),V2) -> a__U52(a__isNatList(V2))
            a__U52(X) -> U52(X)
            a__U52(tt()) -> tt()
            a__U61(X1,X2,X3) -> U61(X1,X2,X3)
            a__U61(tt(),L,N) -> a__U62(a__isNat(N),L)
            a__U62(X1,X2) -> U62(X1,X2)
            a__U62(tt(),L) -> s(a__length(mark(L)))
            a__isNat(X) -> isNat(X)
            a__isNat(0()) -> tt()
            a__isNat(length(V1)) -> a__U11(a__isNatList(V1))
            a__isNat(s(V1)) -> a__U21(a__isNat(V1))
            a__isNatIList(V) -> a__U31(a__isNatList(V))
            a__isNatIList(X) -> isNatIList(X)
            a__isNatIList(cons(V1,V2)) -> a__U41(a__isNat(V1),V2)
            a__isNatIList(zeros()) -> tt()
            a__isNatList(X) -> isNatList(X)
            a__isNatList(cons(V1,V2)) -> a__U51(a__isNat(V1),V2)
            a__isNatList(nil()) -> tt()
            a__length(X) -> length(X)
            a__length(cons(N,L)) -> a__U61(a__isNatList(L),L,N)
            a__length(nil()) -> 0()
            a__zeros() -> cons(0(),zeros())
            a__zeros() -> zeros()
            mark(0()) -> 0()
            mark(U11(X)) -> a__U11(mark(X))
            mark(U21(X)) -> a__U21(mark(X))
            mark(U31(X)) -> a__U31(mark(X))
            mark(U41(X1,X2)) -> a__U41(mark(X1),X2)
            mark(U42(X)) -> a__U42(mark(X))
            mark(U51(X1,X2)) -> a__U51(mark(X1),X2)
            mark(U52(X)) -> a__U52(mark(X))
            mark(U61(X1,X2,X3)) -> a__U61(mark(X1),X2,X3)
            mark(U62(X1,X2)) -> a__U62(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__U11/1,a__U21/1,a__U31/1,a__U41/2,a__U42/1,a__U51/2,a__U52/1,a__U61/3,a__U62/2,a__isNat/1,a__isNatIList/1
            ,a__isNatList/1,a__length/1,a__zeros/0,mark/1} / {0/0,U11/1,U21/1,U31/1,U41/2,U42/1,U51/2,U52/1,U61/3,U62/2
            ,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__U21,a__U31,a__U41,a__U42,a__U51,a__U52,a__U61
            ,a__U62,a__isNat,a__isNatIList,a__isNatList,a__length,a__zeros,mark} and constructors {0,U11,U21,U31,U41,U42
            ,U51,U52,U61,U62,cons,isNat,isNatIList,isNatList,length,nil,s,tt,zeros}
    + Applied Processor:
        DecreasingLoops {bound = AnyLoop, narrow = 10}
    + Details:
        The system has following decreasing Loops:
          a__isNat(x){x -> s(x)} =
            a__isNat(s(x)) ->^+ a__U21(a__isNat(x))
              = C[a__isNat(x) = a__isNat(x){}]

WORST_CASE(Omega(n^1),?)