TIMEOUT
MAYBE
Trs:
 {       cons(mark(X1), X2) -> cons(X1, X2),
       cons(active(X1), X2) -> cons(X1, X2),
         cons(X1, mark(X2)) -> cons(X1, X2),
       cons(X1, active(X2)) -> cons(X1, X2),
              incr(mark(X)) -> incr(X),
            incr(active(X)) -> incr(X),
                 s(mark(X)) -> s(X),
               s(active(X)) -> s(X),
              head(mark(X)) -> head(X),
            head(active(X)) -> head(X),
               mark(nats()) -> active(nats()),
                  mark(0()) -> active(0()),
              mark(pairs()) -> active(pairs()),
               mark(odds()) -> active(odds()),
         mark(cons(X1, X2)) -> active(cons(mark(X1), X2)),
              mark(incr(X)) -> active(incr(mark(X))),
                 mark(s(X)) -> active(s(mark(X))),
              mark(head(X)) -> active(head(mark(X))),
              mark(tail(X)) -> active(tail(mark(X))),
             active(nats()) -> mark(cons(0(), incr(nats()))),
            active(pairs()) -> mark(cons(0(), incr(odds()))),
             active(odds()) -> mark(incr(pairs())),
  active(incr(cons(X, XS))) -> mark(cons(s(X), incr(XS))),
  active(head(cons(X, XS))) -> mark(X),
  active(tail(cons(X, XS))) -> mark(XS),
              tail(mark(X)) -> tail(X),
            tail(active(X)) -> tail(X)}
 Open