MAYBE
MAYBE
TRS:
 {
      U12(tt()) -> U13(isNatKind()),
    isNatKind() -> tt(),
    isNatKind() -> U31(isNatKind()),
    isNatKind() -> U41(isNatKind()),
      U11(tt()) -> U12(isNatKind()),
      U13(tt()) -> U14(isNatKind()),
      U14(tt()) -> U15(isNat()),
      U15(tt()) -> U16(isNat()),
        isNat() -> U11(isNatKind()),
        isNat() -> tt(),
        isNat() -> U21(isNatKind()),
      U16(tt()) -> tt(),
      U22(tt()) -> U23(isNat()),
      U21(tt()) -> U22(isNatKind()),
      U23(tt()) -> tt(),
      U32(tt()) -> tt(),
      U31(tt()) -> U32(isNatKind()),
      U41(tt()) -> tt(),
      U52(tt()) -> N,
      U51(tt()) -> U52(isNatKind()),
      U62(tt()) -> U63(isNat()),
      U61(tt()) -> U62(isNatKind()),
      U63(tt()) -> U64(isNatKind()),
      U64(tt()) -> s(plus(N, M)),
  plus(N, s(M)) -> U61(isNat()),
   plus(N, 0()) -> U51(isNat())
 }
 DUP: We consider a duplicating system.
  Trs:
   {
        U12(tt()) -> U13(isNatKind()),
      isNatKind() -> tt(),
      isNatKind() -> U31(isNatKind()),
      isNatKind() -> U41(isNatKind()),
        U11(tt()) -> U12(isNatKind()),
        U13(tt()) -> U14(isNatKind()),
        U14(tt()) -> U15(isNat()),
        U15(tt()) -> U16(isNat()),
          isNat() -> U11(isNatKind()),
          isNat() -> tt(),
          isNat() -> U21(isNatKind()),
        U16(tt()) -> tt(),
        U22(tt()) -> U23(isNat()),
        U21(tt()) -> U22(isNatKind()),
        U23(tt()) -> tt(),
        U32(tt()) -> tt(),
        U31(tt()) -> U32(isNatKind()),
        U41(tt()) -> tt(),
        U52(tt()) -> N,
        U51(tt()) -> U52(isNatKind()),
        U62(tt()) -> U63(isNat()),
        U61(tt()) -> U62(isNatKind()),
        U63(tt()) -> U64(isNatKind()),
        U64(tt()) -> s(plus(N, M)),
    plus(N, s(M)) -> U61(isNat()),
     plus(N, 0()) -> U51(isNat())
   }
  Fail