MAYBE
MAYBE
TRS:
 {
                      mark(nil()) -> active(nil()),
              mark(first(X1, X2)) -> active(first(mark(X1), mark(X2))),
                        mark(0()) -> active(0()),
               mark(cons(X1, X2)) -> active(cons(mark(X1), X2)),
                       mark(s(X)) -> active(s(mark(X))),
                    mark(from(X)) -> active(from(mark(X))),
            active(first(0(), X)) -> mark(nil()),
  active(first(s(X), cons(Y, Z))) -> mark(cons(Y, first(X, Z))),
                  active(from(X)) -> mark(cons(X, from(s(X)))),
              first(X1, mark(X2)) -> first(X1, X2),
            first(X1, active(X2)) -> first(X1, X2),
              first(mark(X1), X2) -> first(X1, X2),
            first(active(X1), X2) -> first(X1, X2),
               cons(X1, mark(X2)) -> cons(X1, X2),
             cons(X1, active(X2)) -> cons(X1, X2),
               cons(mark(X1), X2) -> cons(X1, X2),
             cons(active(X1), X2) -> cons(X1, X2),
                       s(mark(X)) -> s(X),
                     s(active(X)) -> s(X),
                    from(mark(X)) -> from(X),
                  from(active(X)) -> from(X)
 }
 DUP: We consider a duplicating system.
  Trs:
   {
                        mark(nil()) -> active(nil()),
                mark(first(X1, X2)) -> active(first(mark(X1), mark(X2))),
                          mark(0()) -> active(0()),
                 mark(cons(X1, X2)) -> active(cons(mark(X1), X2)),
                         mark(s(X)) -> active(s(mark(X))),
                      mark(from(X)) -> active(from(mark(X))),
              active(first(0(), X)) -> mark(nil()),
    active(first(s(X), cons(Y, Z))) -> mark(cons(Y, first(X, Z))),
                    active(from(X)) -> mark(cons(X, from(s(X)))),
                first(X1, mark(X2)) -> first(X1, X2),
              first(X1, active(X2)) -> first(X1, X2),
                first(mark(X1), X2) -> first(X1, X2),
              first(active(X1), X2) -> first(X1, X2),
                 cons(X1, mark(X2)) -> cons(X1, X2),
               cons(X1, active(X2)) -> cons(X1, X2),
                 cons(mark(X1), X2) -> cons(X1, X2),
               cons(active(X1), X2) -> cons(X1, X2),
                         s(mark(X)) -> s(X),
                       s(active(X)) -> s(X),
                      from(mark(X)) -> from(X),
                    from(active(X)) -> from(X)
   }
  Fail