MAYBE
MAYBE
TRS:
 {
                 mark(U12(X)) -> active(U12(mark(X))),
               mark(isNat(X)) -> active(isNat(X)),
            mark(U11(X1, X2)) -> active(U11(mark(X1), X2)),
                   mark(tt()) -> active(tt()),
                 mark(U21(X)) -> active(U21(mark(X))),
            mark(U31(X1, X2)) -> active(U31(mark(X1), X2)),
        mark(U42(X1, X2, X3)) -> active(U42(mark(X1), X2, X3)),
        mark(U41(X1, X2, X3)) -> active(U41(mark(X1), X2, X3)),
                   mark(s(X)) -> active(s(mark(X))),
           mark(plus(X1, X2)) -> active(plus(mark(X1), mark(X2))),
                    mark(0()) -> active(0()),
                 U12(mark(X)) -> U12(X),
               U12(active(X)) -> U12(X),
               isNat(mark(X)) -> isNat(X),
             isNat(active(X)) -> isNat(X),
            active(U12(tt())) -> mark(tt()),
         active(isNat(s(V1))) -> mark(U21(isNat(V1))),
  active(isNat(plus(V1, V2))) -> mark(U11(isNat(V1), V2)),
           active(isNat(0())) -> mark(tt()),
        active(U11(tt(), V2)) -> mark(U12(isNat(V2))),
            active(U21(tt())) -> mark(tt()),
         active(U31(tt(), N)) -> mark(N),
      active(U42(tt(), M, N)) -> mark(s(plus(N, M))),
      active(U41(tt(), M, N)) -> mark(U42(isNat(N), M, N)),
        active(plus(N, s(M))) -> mark(U41(isNat(M), M, N)),
         active(plus(N, 0())) -> mark(U31(isNat(N), N)),
            U11(X1, mark(X2)) -> U11(X1, X2),
          U11(X1, active(X2)) -> U11(X1, X2),
            U11(mark(X1), X2) -> U11(X1, X2),
          U11(active(X1), X2) -> U11(X1, X2),
                 U21(mark(X)) -> U21(X),
               U21(active(X)) -> U21(X),
            U31(X1, mark(X2)) -> U31(X1, X2),
          U31(X1, active(X2)) -> U31(X1, X2),
            U31(mark(X1), X2) -> U31(X1, X2),
          U31(active(X1), X2) -> U31(X1, X2),
        U42(X1, X2, mark(X3)) -> U42(X1, X2, X3),
      U42(X1, X2, active(X3)) -> U42(X1, X2, X3),
        U42(X1, mark(X2), X3) -> U42(X1, X2, X3),
      U42(X1, active(X2), X3) -> U42(X1, X2, X3),
        U42(mark(X1), X2, X3) -> U42(X1, X2, X3),
      U42(active(X1), X2, X3) -> U42(X1, X2, X3),
        U41(X1, X2, mark(X3)) -> U41(X1, X2, X3),
      U41(X1, X2, active(X3)) -> U41(X1, X2, X3),
        U41(X1, mark(X2), X3) -> U41(X1, X2, X3),
      U41(X1, active(X2), X3) -> U41(X1, X2, X3),
        U41(mark(X1), X2, X3) -> U41(X1, X2, X3),
      U41(active(X1), X2, X3) -> U41(X1, X2, X3),
                   s(mark(X)) -> s(X),
                 s(active(X)) -> s(X),
           plus(X1, mark(X2)) -> plus(X1, X2),
         plus(X1, active(X2)) -> plus(X1, X2),
           plus(mark(X1), X2) -> plus(X1, X2),
         plus(active(X1), X2) -> plus(X1, X2)
 }
 DUP: We consider a duplicating system.
  Trs:
   {
                   mark(U12(X)) -> active(U12(mark(X))),
                 mark(isNat(X)) -> active(isNat(X)),
              mark(U11(X1, X2)) -> active(U11(mark(X1), X2)),
                     mark(tt()) -> active(tt()),
                   mark(U21(X)) -> active(U21(mark(X))),
              mark(U31(X1, X2)) -> active(U31(mark(X1), X2)),
          mark(U42(X1, X2, X3)) -> active(U42(mark(X1), X2, X3)),
          mark(U41(X1, X2, X3)) -> active(U41(mark(X1), X2, X3)),
                     mark(s(X)) -> active(s(mark(X))),
             mark(plus(X1, X2)) -> active(plus(mark(X1), mark(X2))),
                      mark(0()) -> active(0()),
                   U12(mark(X)) -> U12(X),
                 U12(active(X)) -> U12(X),
                 isNat(mark(X)) -> isNat(X),
               isNat(active(X)) -> isNat(X),
              active(U12(tt())) -> mark(tt()),
           active(isNat(s(V1))) -> mark(U21(isNat(V1))),
    active(isNat(plus(V1, V2))) -> mark(U11(isNat(V1), V2)),
             active(isNat(0())) -> mark(tt()),
          active(U11(tt(), V2)) -> mark(U12(isNat(V2))),
              active(U21(tt())) -> mark(tt()),
           active(U31(tt(), N)) -> mark(N),
        active(U42(tt(), M, N)) -> mark(s(plus(N, M))),
        active(U41(tt(), M, N)) -> mark(U42(isNat(N), M, N)),
          active(plus(N, s(M))) -> mark(U41(isNat(M), M, N)),
           active(plus(N, 0())) -> mark(U31(isNat(N), N)),
              U11(X1, mark(X2)) -> U11(X1, X2),
            U11(X1, active(X2)) -> U11(X1, X2),
              U11(mark(X1), X2) -> U11(X1, X2),
            U11(active(X1), X2) -> U11(X1, X2),
                   U21(mark(X)) -> U21(X),
                 U21(active(X)) -> U21(X),
              U31(X1, mark(X2)) -> U31(X1, X2),
            U31(X1, active(X2)) -> U31(X1, X2),
              U31(mark(X1), X2) -> U31(X1, X2),
            U31(active(X1), X2) -> U31(X1, X2),
          U42(X1, X2, mark(X3)) -> U42(X1, X2, X3),
        U42(X1, X2, active(X3)) -> U42(X1, X2, X3),
          U42(X1, mark(X2), X3) -> U42(X1, X2, X3),
        U42(X1, active(X2), X3) -> U42(X1, X2, X3),
          U42(mark(X1), X2, X3) -> U42(X1, X2, X3),
        U42(active(X1), X2, X3) -> U42(X1, X2, X3),
          U41(X1, X2, mark(X3)) -> U41(X1, X2, X3),
        U41(X1, X2, active(X3)) -> U41(X1, X2, X3),
          U41(X1, mark(X2), X3) -> U41(X1, X2, X3),
        U41(X1, active(X2), X3) -> U41(X1, X2, X3),
          U41(mark(X1), X2, X3) -> U41(X1, X2, X3),
        U41(active(X1), X2, X3) -> U41(X1, X2, X3),
                     s(mark(X)) -> s(X),
                   s(active(X)) -> s(X),
             plus(X1, mark(X2)) -> plus(X1, X2),
           plus(X1, active(X2)) -> plus(X1, X2),
             plus(mark(X1), X2) -> plus(X1, X2),
           plus(active(X1), X2) -> plus(X1, X2)
   }
  Fail