MAYBE
MAYBE
TRS:
 {
                  U12(tt()) -> tt(),
              isNat(n__0()) -> tt(),
     isNat(n__plus(V1, V2)) -> U11(isNat(activate(V1)), activate(V2)),
            isNat(n__s(V1)) -> U21(isNat(activate(V1))),
                activate(X) -> X,
           activate(n__0()) -> 0(),
  activate(n__plus(X1, X2)) -> plus(activate(X1), activate(X2)),
          activate(n__s(X)) -> s(activate(X)),
              U11(tt(), V2) -> U12(isNat(activate(V2))),
                  U21(tt()) -> tt(),
               U31(tt(), N) -> activate(N),
            U42(tt(), M, N) -> s(plus(activate(N), activate(M))),
            U41(tt(), M, N) ->
  U42(isNat(activate(N)), activate(M), activate(N)),
                       s(X) -> n__s(X),
              plus(N, s(M)) -> U41(isNat(M), M, N),
               plus(N, 0()) -> U31(isNat(N), N),
               plus(X1, X2) -> n__plus(X1, X2),
                        0() -> n__0()
 }
 DUP: We consider a duplicating system.
  Trs:
   {
                    U12(tt()) -> tt(),
                isNat(n__0()) -> tt(),
       isNat(n__plus(V1, V2)) -> U11(isNat(activate(V1)), activate(V2)),
              isNat(n__s(V1)) -> U21(isNat(activate(V1))),
                  activate(X) -> X,
             activate(n__0()) -> 0(),
    activate(n__plus(X1, X2)) -> plus(activate(X1), activate(X2)),
            activate(n__s(X)) -> s(activate(X)),
                U11(tt(), V2) -> U12(isNat(activate(V2))),
                    U21(tt()) -> tt(),
                 U31(tt(), N) -> activate(N),
              U42(tt(), M, N) -> s(plus(activate(N), activate(M))),
              U41(tt(), M, N) ->
    U42(isNat(activate(N)), activate(M), activate(N)),
                         s(X) -> n__s(X),
                plus(N, s(M)) -> U41(isNat(M), M, N),
                 plus(N, 0()) -> U31(isNat(N), N),
                 plus(X1, X2) -> n__plus(X1, X2),
                          0() -> n__0()
   }
  Fail