MAYBE MAYBE TRS: { mark(U12(X1, X2, X3)) -> active(U12(mark(X1), X2, X3)), mark(tt()) -> active(tt()), mark(U11(X1, X2, X3)) -> active(U11(mark(X1), X2, X3)), mark(snd(X)) -> active(snd(mark(X))), mark(splitAt(X1, X2)) -> active(splitAt(mark(X1), mark(X2))), mark(U22(X1, X2)) -> active(U22(mark(X1), X2)), mark(U21(X1, X2)) -> active(U21(mark(X1), X2)), mark(U32(X1, X2)) -> active(U32(mark(X1), X2)), 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(head(X)) -> active(head(mark(X))), mark(afterNth(X1, X2)) -> active(afterNth(mark(X1), mark(X2))), mark(U52(X1, X2)) -> active(U52(mark(X1), X2)), mark(U51(X1, X2)) -> active(U51(mark(X1), X2)), mark(U62(X1, X2, X3, X4)) -> active(U62(mark(X1), X2, X3, X4)), mark(U61(X1, X2, X3, X4)) -> active(U61(mark(X1), X2, X3, X4)), mark(U63(X1, X2, X3, X4)) -> active(U63(mark(X1), X2, X3, X4)), mark(U64(X1, X2)) -> active(U64(mark(X1), X2)), mark(pair(X1, X2)) -> active(pair(mark(X1), mark(X2))), mark(cons(X1, X2)) -> active(cons(mark(X1), X2)), mark(U72(X1, X2)) -> active(U72(mark(X1), X2)), mark(U71(X1, X2)) -> active(U71(mark(X1), X2)), mark(U82(X1, X2, X3)) -> active(U82(mark(X1), X2, X3)), mark(U81(X1, X2, X3)) -> active(U81(mark(X1), X2, X3)), mark(fst(X)) -> active(fst(mark(X))), mark(natsFrom(X)) -> active(natsFrom(mark(X))), mark(s(X)) -> active(s(mark(X))), mark(sel(X1, X2)) -> active(sel(mark(X1), mark(X2))), mark(nil()) -> active(nil()), mark(0()) -> active(0()), mark(tail(X)) -> active(tail(mark(X))), mark(take(X1, X2)) -> active(take(mark(X1), mark(X2))), U12(X1, X2, mark(X3)) -> U12(X1, X2, X3), U12(X1, X2, active(X3)) -> U12(X1, X2, X3), U12(X1, mark(X2), X3) -> U12(X1, X2, X3), U12(X1, active(X2), X3) -> U12(X1, X2, X3), U12(mark(X1), X2, X3) -> U12(X1, X2, X3), U12(active(X1), X2, X3) -> U12(X1, X2, X3), active(U12(tt(), N, XS)) -> mark(snd(splitAt(N, XS))), active(U11(tt(), N, XS)) -> mark(U12(tt(), N, XS)), active(snd(pair(X, Y))) -> mark(U51(tt(), Y)), active(splitAt(s(N), cons(X, XS))) -> mark(U61(tt(), N, X, XS)), active(splitAt(0(), XS)) -> mark(pair(nil(), XS)), active(U22(tt(), X)) -> mark(X), active(U21(tt(), X)) -> mark(U22(tt(), X)), active(U32(tt(), N)) -> mark(N), active(U31(tt(), N)) -> mark(U32(tt(), N)), active(U42(tt(), N, XS)) -> mark(head(afterNth(N, XS))), active(U41(tt(), N, XS)) -> mark(U42(tt(), N, XS)), active(head(cons(N, XS))) -> mark(U31(tt(), N)), active(afterNth(N, XS)) -> mark(U11(tt(), N, XS)), active(U52(tt(), Y)) -> mark(Y), active(U51(tt(), Y)) -> mark(U52(tt(), Y)), active(U62(tt(), N, X, XS)) -> mark(U63(tt(), N, X, XS)), active(U61(tt(), N, X, XS)) -> mark(U62(tt(), N, X, XS)), active(U63(tt(), N, X, XS)) -> mark(U64(splitAt(N, XS), X)), active(U64(pair(YS, ZS), X)) -> mark(pair(cons(X, YS), ZS)), active(U72(tt(), XS)) -> mark(XS), active(U71(tt(), XS)) -> mark(U72(tt(), XS)), active(U82(tt(), N, XS)) -> mark(fst(splitAt(N, XS))), active(U81(tt(), N, XS)) -> mark(U82(tt(), N, XS)), active(fst(pair(X, Y))) -> mark(U21(tt(), X)), active(natsFrom(N)) -> mark(cons(N, natsFrom(s(N)))), active(sel(N, XS)) -> mark(U41(tt(), N, XS)), active(tail(cons(N, XS))) -> mark(U71(tt(), XS)), active(take(N, XS)) -> mark(U81(tt(), N, XS)), U11(X1, X2, mark(X3)) -> U11(X1, X2, X3), U11(X1, X2, active(X3)) -> U11(X1, X2, X3), U11(X1, mark(X2), X3) -> U11(X1, X2, X3), U11(X1, active(X2), X3) -> U11(X1, X2, X3), U11(mark(X1), X2, X3) -> U11(X1, X2, X3), U11(active(X1), X2, X3) -> U11(X1, X2, X3), snd(mark(X)) -> snd(X), snd(active(X)) -> snd(X), splitAt(X1, mark(X2)) -> splitAt(X1, X2), splitAt(X1, active(X2)) -> splitAt(X1, X2), splitAt(mark(X1), X2) -> splitAt(X1, X2), splitAt(active(X1), X2) -> splitAt(X1, X2), U22(X1, mark(X2)) -> U22(X1, X2), U22(X1, active(X2)) -> U22(X1, X2), U22(mark(X1), X2) -> U22(X1, X2), U22(active(X1), X2) -> U22(X1, X2), U21(X1, mark(X2)) -> U21(X1, X2), U21(X1, active(X2)) -> U21(X1, X2), U21(mark(X1), X2) -> U21(X1, X2), U21(active(X1), X2) -> U21(X1, X2), U32(X1, mark(X2)) -> U32(X1, X2), U32(X1, active(X2)) -> U32(X1, X2), U32(mark(X1), X2) -> U32(X1, X2), U32(active(X1), X2) -> U32(X1, X2), 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), head(mark(X)) -> head(X), head(active(X)) -> head(X), afterNth(X1, mark(X2)) -> afterNth(X1, X2), afterNth(X1, active(X2)) -> afterNth(X1, X2), afterNth(mark(X1), X2) -> afterNth(X1, X2), afterNth(active(X1), X2) -> afterNth(X1, X2), U52(X1, mark(X2)) -> U52(X1, X2), U52(X1, active(X2)) -> U52(X1, X2), U52(mark(X1), X2) -> U52(X1, X2), U52(active(X1), X2) -> U52(X1, X2), U51(X1, mark(X2)) -> U51(X1, X2), U51(X1, active(X2)) -> U51(X1, X2), U51(mark(X1), X2) -> U51(X1, X2), U51(active(X1), X2) -> U51(X1, X2), U62(X1, X2, X3, mark(X4)) -> U62(X1, X2, X3, X4), U62(X1, X2, X3, active(X4)) -> U62(X1, X2, X3, X4), U62(X1, X2, mark(X3), X4) -> U62(X1, X2, X3, X4), U62(X1, X2, active(X3), X4) -> U62(X1, X2, X3, X4), U62(X1, mark(X2), X3, X4) -> U62(X1, X2, X3, X4), U62(X1, active(X2), X3, X4) -> U62(X1, X2, X3, X4), U62(mark(X1), X2, X3, X4) -> U62(X1, X2, X3, X4), U62(active(X1), X2, X3, X4) -> U62(X1, X2, X3, X4), U61(X1, X2, X3, mark(X4)) -> U61(X1, X2, X3, X4), U61(X1, X2, X3, active(X4)) -> U61(X1, X2, X3, X4), U61(X1, X2, mark(X3), X4) -> U61(X1, X2, X3, X4), U61(X1, X2, active(X3), X4) -> U61(X1, X2, X3, X4), U61(X1, mark(X2), X3, X4) -> U61(X1, X2, X3, X4), U61(X1, active(X2), X3, X4) -> U61(X1, X2, X3, X4), U61(mark(X1), X2, X3, X4) -> U61(X1, X2, X3, X4), U61(active(X1), X2, X3, X4) -> U61(X1, X2, X3, X4), U63(X1, X2, X3, mark(X4)) -> U63(X1, X2, X3, X4), U63(X1, X2, X3, active(X4)) -> U63(X1, X2, X3, X4), U63(X1, X2, mark(X3), X4) -> U63(X1, X2, X3, X4), U63(X1, X2, active(X3), X4) -> U63(X1, X2, X3, X4), U63(X1, mark(X2), X3, X4) -> U63(X1, X2, X3, X4), U63(X1, active(X2), X3, X4) -> U63(X1, X2, X3, X4), U63(mark(X1), X2, X3, X4) -> U63(X1, X2, X3, X4), U63(active(X1), X2, X3, X4) -> U63(X1, X2, X3, X4), U64(X1, mark(X2)) -> U64(X1, X2), U64(X1, active(X2)) -> U64(X1, X2), U64(mark(X1), X2) -> U64(X1, X2), U64(active(X1), X2) -> U64(X1, X2), pair(X1, mark(X2)) -> pair(X1, X2), pair(X1, active(X2)) -> pair(X1, X2), pair(mark(X1), X2) -> pair(X1, X2), pair(active(X1), X2) -> pair(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), U72(X1, mark(X2)) -> U72(X1, X2), U72(X1, active(X2)) -> U72(X1, X2), U72(mark(X1), X2) -> U72(X1, X2), U72(active(X1), X2) -> U72(X1, X2), U71(X1, mark(X2)) -> U71(X1, X2), U71(X1, active(X2)) -> U71(X1, X2), U71(mark(X1), X2) -> U71(X1, X2), U71(active(X1), X2) -> U71(X1, X2), U82(X1, X2, mark(X3)) -> U82(X1, X2, X3), U82(X1, X2, active(X3)) -> U82(X1, X2, X3), U82(X1, mark(X2), X3) -> U82(X1, X2, X3), U82(X1, active(X2), X3) -> U82(X1, X2, X3), U82(mark(X1), X2, X3) -> U82(X1, X2, X3), U82(active(X1), X2, X3) -> U82(X1, X2, X3), U81(X1, X2, mark(X3)) -> U81(X1, X2, X3), U81(X1, X2, active(X3)) -> U81(X1, X2, X3), U81(X1, mark(X2), X3) -> U81(X1, X2, X3), U81(X1, active(X2), X3) -> U81(X1, X2, X3), U81(mark(X1), X2, X3) -> U81(X1, X2, X3), U81(active(X1), X2, X3) -> U81(X1, X2, X3), fst(mark(X)) -> fst(X), fst(active(X)) -> fst(X), natsFrom(mark(X)) -> natsFrom(X), natsFrom(active(X)) -> natsFrom(X), s(mark(X)) -> s(X), s(active(X)) -> s(X), sel(X1, mark(X2)) -> sel(X1, X2), sel(X1, active(X2)) -> sel(X1, X2), sel(mark(X1), X2) -> sel(X1, X2), sel(active(X1), X2) -> sel(X1, X2), tail(mark(X)) -> tail(X), tail(active(X)) -> tail(X), take(X1, mark(X2)) -> take(X1, X2), take(X1, active(X2)) -> take(X1, X2), take(mark(X1), X2) -> take(X1, X2), take(active(X1), X2) -> take(X1, X2) } DUP: We consider a duplicating system. Trs: { mark(U12(X1, X2, X3)) -> active(U12(mark(X1), X2, X3)), mark(tt()) -> active(tt()), mark(U11(X1, X2, X3)) -> active(U11(mark(X1), X2, X3)), mark(snd(X)) -> active(snd(mark(X))), mark(splitAt(X1, X2)) -> active(splitAt(mark(X1), mark(X2))), mark(U22(X1, X2)) -> active(U22(mark(X1), X2)), mark(U21(X1, X2)) -> active(U21(mark(X1), X2)), mark(U32(X1, X2)) -> active(U32(mark(X1), X2)), 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(head(X)) -> active(head(mark(X))), mark(afterNth(X1, X2)) -> active(afterNth(mark(X1), mark(X2))), mark(U52(X1, X2)) -> active(U52(mark(X1), X2)), mark(U51(X1, X2)) -> active(U51(mark(X1), X2)), mark(U62(X1, X2, X3, X4)) -> active(U62(mark(X1), X2, X3, X4)), mark(U61(X1, X2, X3, X4)) -> active(U61(mark(X1), X2, X3, X4)), mark(U63(X1, X2, X3, X4)) -> active(U63(mark(X1), X2, X3, X4)), mark(U64(X1, X2)) -> active(U64(mark(X1), X2)), mark(pair(X1, X2)) -> active(pair(mark(X1), mark(X2))), mark(cons(X1, X2)) -> active(cons(mark(X1), X2)), mark(U72(X1, X2)) -> active(U72(mark(X1), X2)), mark(U71(X1, X2)) -> active(U71(mark(X1), X2)), mark(U82(X1, X2, X3)) -> active(U82(mark(X1), X2, X3)), mark(U81(X1, X2, X3)) -> active(U81(mark(X1), X2, X3)), mark(fst(X)) -> active(fst(mark(X))), mark(natsFrom(X)) -> active(natsFrom(mark(X))), mark(s(X)) -> active(s(mark(X))), mark(sel(X1, X2)) -> active(sel(mark(X1), mark(X2))), mark(nil()) -> active(nil()), mark(0()) -> active(0()), mark(tail(X)) -> active(tail(mark(X))), mark(take(X1, X2)) -> active(take(mark(X1), mark(X2))), U12(X1, X2, mark(X3)) -> U12(X1, X2, X3), U12(X1, X2, active(X3)) -> U12(X1, X2, X3), U12(X1, mark(X2), X3) -> U12(X1, X2, X3), U12(X1, active(X2), X3) -> U12(X1, X2, X3), U12(mark(X1), X2, X3) -> U12(X1, X2, X3), U12(active(X1), X2, X3) -> U12(X1, X2, X3), active(U12(tt(), N, XS)) -> mark(snd(splitAt(N, XS))), active(U11(tt(), N, XS)) -> mark(U12(tt(), N, XS)), active(snd(pair(X, Y))) -> mark(U51(tt(), Y)), active(splitAt(s(N), cons(X, XS))) -> mark(U61(tt(), N, X, XS)), active(splitAt(0(), XS)) -> mark(pair(nil(), XS)), active(U22(tt(), X)) -> mark(X), active(U21(tt(), X)) -> mark(U22(tt(), X)), active(U32(tt(), N)) -> mark(N), active(U31(tt(), N)) -> mark(U32(tt(), N)), active(U42(tt(), N, XS)) -> mark(head(afterNth(N, XS))), active(U41(tt(), N, XS)) -> mark(U42(tt(), N, XS)), active(head(cons(N, XS))) -> mark(U31(tt(), N)), active(afterNth(N, XS)) -> mark(U11(tt(), N, XS)), active(U52(tt(), Y)) -> mark(Y), active(U51(tt(), Y)) -> mark(U52(tt(), Y)), active(U62(tt(), N, X, XS)) -> mark(U63(tt(), N, X, XS)), active(U61(tt(), N, X, XS)) -> mark(U62(tt(), N, X, XS)), active(U63(tt(), N, X, XS)) -> mark(U64(splitAt(N, XS), X)), active(U64(pair(YS, ZS), X)) -> mark(pair(cons(X, YS), ZS)), active(U72(tt(), XS)) -> mark(XS), active(U71(tt(), XS)) -> mark(U72(tt(), XS)), active(U82(tt(), N, XS)) -> mark(fst(splitAt(N, XS))), active(U81(tt(), N, XS)) -> mark(U82(tt(), N, XS)), active(fst(pair(X, Y))) -> mark(U21(tt(), X)), active(natsFrom(N)) -> mark(cons(N, natsFrom(s(N)))), active(sel(N, XS)) -> mark(U41(tt(), N, XS)), active(tail(cons(N, XS))) -> mark(U71(tt(), XS)), active(take(N, XS)) -> mark(U81(tt(), N, XS)), U11(X1, X2, mark(X3)) -> U11(X1, X2, X3), U11(X1, X2, active(X3)) -> U11(X1, X2, X3), U11(X1, mark(X2), X3) -> U11(X1, X2, X3), U11(X1, active(X2), X3) -> U11(X1, X2, X3), U11(mark(X1), X2, X3) -> U11(X1, X2, X3), U11(active(X1), X2, X3) -> U11(X1, X2, X3), snd(mark(X)) -> snd(X), snd(active(X)) -> snd(X), splitAt(X1, mark(X2)) -> splitAt(X1, X2), splitAt(X1, active(X2)) -> splitAt(X1, X2), splitAt(mark(X1), X2) -> splitAt(X1, X2), splitAt(active(X1), X2) -> splitAt(X1, X2), U22(X1, mark(X2)) -> U22(X1, X2), U22(X1, active(X2)) -> U22(X1, X2), U22(mark(X1), X2) -> U22(X1, X2), U22(active(X1), X2) -> U22(X1, X2), U21(X1, mark(X2)) -> U21(X1, X2), U21(X1, active(X2)) -> U21(X1, X2), U21(mark(X1), X2) -> U21(X1, X2), U21(active(X1), X2) -> U21(X1, X2), U32(X1, mark(X2)) -> U32(X1, X2), U32(X1, active(X2)) -> U32(X1, X2), U32(mark(X1), X2) -> U32(X1, X2), U32(active(X1), X2) -> U32(X1, X2), 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), head(mark(X)) -> head(X), head(active(X)) -> head(X), afterNth(X1, mark(X2)) -> afterNth(X1, X2), afterNth(X1, active(X2)) -> afterNth(X1, X2), afterNth(mark(X1), X2) -> afterNth(X1, X2), afterNth(active(X1), X2) -> afterNth(X1, X2), U52(X1, mark(X2)) -> U52(X1, X2), U52(X1, active(X2)) -> U52(X1, X2), U52(mark(X1), X2) -> U52(X1, X2), U52(active(X1), X2) -> U52(X1, X2), U51(X1, mark(X2)) -> U51(X1, X2), U51(X1, active(X2)) -> U51(X1, X2), U51(mark(X1), X2) -> U51(X1, X2), U51(active(X1), X2) -> U51(X1, X2), U62(X1, X2, X3, mark(X4)) -> U62(X1, X2, X3, X4), U62(X1, X2, X3, active(X4)) -> U62(X1, X2, X3, X4), U62(X1, X2, mark(X3), X4) -> U62(X1, X2, X3, X4), U62(X1, X2, active(X3), X4) -> U62(X1, X2, X3, X4), U62(X1, mark(X2), X3, X4) -> U62(X1, X2, X3, X4), U62(X1, active(X2), X3, X4) -> U62(X1, X2, X3, X4), U62(mark(X1), X2, X3, X4) -> U62(X1, X2, X3, X4), U62(active(X1), X2, X3, X4) -> U62(X1, X2, X3, X4), U61(X1, X2, X3, mark(X4)) -> U61(X1, X2, X3, X4), U61(X1, X2, X3, active(X4)) -> U61(X1, X2, X3, X4), U61(X1, X2, mark(X3), X4) -> U61(X1, X2, X3, X4), U61(X1, X2, active(X3), X4) -> U61(X1, X2, X3, X4), U61(X1, mark(X2), X3, X4) -> U61(X1, X2, X3, X4), U61(X1, active(X2), X3, X4) -> U61(X1, X2, X3, X4), U61(mark(X1), X2, X3, X4) -> U61(X1, X2, X3, X4), U61(active(X1), X2, X3, X4) -> U61(X1, X2, X3, X4), U63(X1, X2, X3, mark(X4)) -> U63(X1, X2, X3, X4), U63(X1, X2, X3, active(X4)) -> U63(X1, X2, X3, X4), U63(X1, X2, mark(X3), X4) -> U63(X1, X2, X3, X4), U63(X1, X2, active(X3), X4) -> U63(X1, X2, X3, X4), U63(X1, mark(X2), X3, X4) -> U63(X1, X2, X3, X4), U63(X1, active(X2), X3, X4) -> U63(X1, X2, X3, X4), U63(mark(X1), X2, X3, X4) -> U63(X1, X2, X3, X4), U63(active(X1), X2, X3, X4) -> U63(X1, X2, X3, X4), U64(X1, mark(X2)) -> U64(X1, X2), U64(X1, active(X2)) -> U64(X1, X2), U64(mark(X1), X2) -> U64(X1, X2), U64(active(X1), X2) -> U64(X1, X2), pair(X1, mark(X2)) -> pair(X1, X2), pair(X1, active(X2)) -> pair(X1, X2), pair(mark(X1), X2) -> pair(X1, X2), pair(active(X1), X2) -> pair(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), U72(X1, mark(X2)) -> U72(X1, X2), U72(X1, active(X2)) -> U72(X1, X2), U72(mark(X1), X2) -> U72(X1, X2), U72(active(X1), X2) -> U72(X1, X2), U71(X1, mark(X2)) -> U71(X1, X2), U71(X1, active(X2)) -> U71(X1, X2), U71(mark(X1), X2) -> U71(X1, X2), U71(active(X1), X2) -> U71(X1, X2), U82(X1, X2, mark(X3)) -> U82(X1, X2, X3), U82(X1, X2, active(X3)) -> U82(X1, X2, X3), U82(X1, mark(X2), X3) -> U82(X1, X2, X3), U82(X1, active(X2), X3) -> U82(X1, X2, X3), U82(mark(X1), X2, X3) -> U82(X1, X2, X3), U82(active(X1), X2, X3) -> U82(X1, X2, X3), U81(X1, X2, mark(X3)) -> U81(X1, X2, X3), U81(X1, X2, active(X3)) -> U81(X1, X2, X3), U81(X1, mark(X2), X3) -> U81(X1, X2, X3), U81(X1, active(X2), X3) -> U81(X1, X2, X3), U81(mark(X1), X2, X3) -> U81(X1, X2, X3), U81(active(X1), X2, X3) -> U81(X1, X2, X3), fst(mark(X)) -> fst(X), fst(active(X)) -> fst(X), natsFrom(mark(X)) -> natsFrom(X), natsFrom(active(X)) -> natsFrom(X), s(mark(X)) -> s(X), s(active(X)) -> s(X), sel(X1, mark(X2)) -> sel(X1, X2), sel(X1, active(X2)) -> sel(X1, X2), sel(mark(X1), X2) -> sel(X1, X2), sel(active(X1), X2) -> sel(X1, X2), tail(mark(X)) -> tail(X), tail(active(X)) -> tail(X), take(X1, mark(X2)) -> take(X1, X2), take(X1, active(X2)) -> take(X1, X2), take(mark(X1), X2) -> take(X1, X2), take(active(X1), X2) -> take(X1, X2) } Fail