(VAR V1 V2 L N IL M V X1 X2 X3 X4 X)
(RULES 
active(zeros) -> mark(cons(0,zeros))
active(U101(tt,V1,V2)) -> mark(U102(isNatKind(V1),V1,V2))
active(U102(tt,V1,V2)) -> mark(U103(isNatIListKind(V2),V1,V2))
active(U103(tt,V1,V2)) -> mark(U104(isNatIListKind(V2),V1,V2))
active(U104(tt,V1,V2)) -> mark(U105(isNat(V1),V2))
active(U105(tt,V2)) -> mark(U106(isNatIList(V2)))
active(U106(tt)) -> mark(tt)
active(U11(tt,V1)) -> mark(U12(isNatIListKind(V1),V1))
active(U111(tt,L,N)) -> mark(U112(isNatIListKind(L),L,N))
active(U112(tt,L,N)) -> mark(U113(isNat(N),L,N))
active(U113(tt,L,N)) -> mark(U114(isNatKind(N),L))
active(U114(tt,L)) -> mark(s(length(L)))
active(U12(tt,V1)) -> mark(U13(isNatList(V1)))
active(U121(tt,IL)) -> mark(U122(isNatIListKind(IL)))
active(U122(tt)) -> mark(nil)
active(U13(tt)) -> mark(tt)
active(U131(tt,IL,M,N)) -> mark(U132(isNatIListKind(IL),IL,M,N))
active(U132(tt,IL,M,N)) -> mark(U133(isNat(M),IL,M,N))
active(U133(tt,IL,M,N)) -> mark(U134(isNatKind(M),IL,M,N))
active(U134(tt,IL,M,N)) -> mark(U135(isNat(N),IL,M,N))
active(U135(tt,IL,M,N)) -> mark(U136(isNatKind(N),IL,M,N))
active(U136(tt,IL,M,N)) -> mark(cons(N,take(M,IL)))
active(U21(tt,V1)) -> mark(U22(isNatKind(V1),V1))
active(U22(tt,V1)) -> mark(U23(isNat(V1)))
active(U23(tt)) -> mark(tt)
active(U31(tt,V)) -> mark(U32(isNatIListKind(V),V))
active(U32(tt,V)) -> mark(U33(isNatList(V)))
active(U33(tt)) -> mark(tt)
active(U41(tt,V1,V2)) -> mark(U42(isNatKind(V1),V1,V2))
active(U42(tt,V1,V2)) -> mark(U43(isNatIListKind(V2),V1,V2))
active(U43(tt,V1,V2)) -> mark(U44(isNatIListKind(V2),V1,V2))
active(U44(tt,V1,V2)) -> mark(U45(isNat(V1),V2))
active(U45(tt,V2)) -> mark(U46(isNatIList(V2)))
active(U46(tt)) -> mark(tt)
active(U51(tt,V2)) -> mark(U52(isNatIListKind(V2)))
active(U52(tt)) -> mark(tt)
active(U61(tt,V2)) -> mark(U62(isNatIListKind(V2)))
active(U62(tt)) -> mark(tt)
active(U71(tt)) -> mark(tt)
active(U81(tt)) -> mark(tt)
active(U91(tt,V1,V2)) -> mark(U92(isNatKind(V1),V1,V2))
active(U92(tt,V1,V2)) -> mark(U93(isNatIListKind(V2),V1,V2))
active(U93(tt,V1,V2)) -> mark(U94(isNatIListKind(V2),V1,V2))
active(U94(tt,V1,V2)) -> mark(U95(isNat(V1),V2))
active(U95(tt,V2)) -> mark(U96(isNatList(V2)))
active(U96(tt)) -> mark(tt)
active(isNat(0)) -> mark(tt)
active(isNat(length(V1))) -> mark(U11(isNatIListKind(V1),V1))
active(isNat(s(V1))) -> mark(U21(isNatKind(V1),V1))
active(isNatIList(V)) -> mark(U31(isNatIListKind(V),V))
active(isNatIList(zeros)) -> mark(tt)
active(isNatIList(cons(V1,V2))) -> mark(U41(isNatKind(V1),V1,V2))
active(isNatIListKind(nil)) -> mark(tt)
active(isNatIListKind(zeros)) -> mark(tt)
active(isNatIListKind(cons(V1,V2))) -> mark(U51(isNatKind(V1),V2))
active(isNatIListKind(take(V1,V2))) -> mark(U61(isNatKind(V1),V2))
active(isNatKind(0)) -> mark(tt)
active(isNatKind(length(V1))) -> mark(U71(isNatIListKind(V1)))
active(isNatKind(s(V1))) -> mark(U81(isNatKind(V1)))
active(isNatList(nil)) -> mark(tt)
active(isNatList(cons(V1,V2))) -> mark(U91(isNatKind(V1),V1,V2))
active(isNatList(take(V1,V2))) -> mark(U101(isNatKind(V1),V1,V2))
active(length(nil)) -> mark(0)
active(length(cons(N,L))) -> mark(U111(isNatList(L),L,N))
active(take(0,IL)) -> mark(U121(isNatIList(IL),IL))
active(take(s(M),cons(N,IL))) -> mark(U131(isNatIList(IL),IL,M,N))
mark(zeros) -> active(zeros)
mark(cons(X1,X2)) -> active(cons(mark(X1),X2))
mark(0) -> active(0)
mark(U101(X1,X2,X3)) -> active(U101(mark(X1),X2,X3))
mark(tt) -> active(tt)
mark(U102(X1,X2,X3)) -> active(U102(mark(X1),X2,X3))
mark(isNatKind(X)) -> active(isNatKind(X))
mark(U103(X1,X2,X3)) -> active(U103(mark(X1),X2,X3))
mark(isNatIListKind(X)) -> active(isNatIListKind(X))
mark(U104(X1,X2,X3)) -> active(U104(mark(X1),X2,X3))
mark(U105(X1,X2)) -> active(U105(mark(X1),X2))
mark(isNat(X)) -> active(isNat(X))
mark(U106(X)) -> active(U106(mark(X)))
mark(isNatIList(X)) -> active(isNatIList(X))
mark(U11(X1,X2)) -> active(U11(mark(X1),X2))
mark(U12(X1,X2)) -> active(U12(mark(X1),X2))
mark(U111(X1,X2,X3)) -> active(U111(mark(X1),X2,X3))
mark(U112(X1,X2,X3)) -> active(U112(mark(X1),X2,X3))
mark(U113(X1,X2,X3)) -> active(U113(mark(X1),X2,X3))
mark(U114(X1,X2)) -> active(U114(mark(X1),X2))
mark(s(X)) -> active(s(mark(X)))
mark(length(X)) -> active(length(mark(X)))
mark(U13(X)) -> active(U13(mark(X)))
mark(isNatList(X)) -> active(isNatList(X))
mark(U121(X1,X2)) -> active(U121(mark(X1),X2))
mark(U122(X)) -> active(U122(mark(X)))
mark(nil) -> active(nil)
mark(U131(X1,X2,X3,X4)) -> active(U131(mark(X1),X2,X3,X4))
mark(U132(X1,X2,X3,X4)) -> active(U132(mark(X1),X2,X3,X4))
mark(U133(X1,X2,X3,X4)) -> active(U133(mark(X1),X2,X3,X4))
mark(U134(X1,X2,X3,X4)) -> active(U134(mark(X1),X2,X3,X4))
mark(U135(X1,X2,X3,X4)) -> active(U135(mark(X1),X2,X3,X4))
mark(U136(X1,X2,X3,X4)) -> active(U136(mark(X1),X2,X3,X4))
mark(take(X1,X2)) -> active(take(mark(X1),mark(X2)))
mark(U21(X1,X2)) -> active(U21(mark(X1),X2))
mark(U22(X1,X2)) -> active(U22(mark(X1),X2))
mark(U23(X)) -> active(U23(mark(X)))
mark(U31(X1,X2)) -> active(U31(mark(X1),X2))
mark(U32(X1,X2)) -> active(U32(mark(X1),X2))
mark(U33(X)) -> active(U33(mark(X)))
mark(U41(X1,X2,X3)) -> active(U41(mark(X1),X2,X3))
mark(U42(X1,X2,X3)) -> active(U42(mark(X1),X2,X3))
mark(U43(X1,X2,X3)) -> active(U43(mark(X1),X2,X3))
mark(U44(X1,X2,X3)) -> active(U44(mark(X1),X2,X3))
mark(U45(X1,X2)) -> active(U45(mark(X1),X2))
mark(U46(X)) -> active(U46(mark(X)))
mark(U51(X1,X2)) -> active(U51(mark(X1),X2))
mark(U52(X)) -> active(U52(mark(X)))
mark(U61(X1,X2)) -> active(U61(mark(X1),X2))
mark(U62(X)) -> active(U62(mark(X)))
mark(U71(X)) -> active(U71(mark(X)))
mark(U81(X)) -> active(U81(mark(X)))
mark(U91(X1,X2,X3)) -> active(U91(mark(X1),X2,X3))
mark(U92(X1,X2,X3)) -> active(U92(mark(X1),X2,X3))
mark(U93(X1,X2,X3)) -> active(U93(mark(X1),X2,X3))
mark(U94(X1,X2,X3)) -> active(U94(mark(X1),X2,X3))
mark(U95(X1,X2)) -> active(U95(mark(X1),X2))
mark(U96(X)) -> active(U96(mark(X)))
cons(mark(X1),X2) -> cons(X1,X2)
cons(X1,mark(X2)) -> cons(X1,X2)
cons(active(X1),X2) -> cons(X1,X2)
cons(X1,active(X2)) -> cons(X1,X2)
U101(mark(X1),X2,X3) -> U101(X1,X2,X3)
U101(X1,mark(X2),X3) -> U101(X1,X2,X3)
U101(X1,X2,mark(X3)) -> U101(X1,X2,X3)
U101(active(X1),X2,X3) -> U101(X1,X2,X3)
U101(X1,active(X2),X3) -> U101(X1,X2,X3)
U101(X1,X2,active(X3)) -> U101(X1,X2,X3)
U102(mark(X1),X2,X3) -> U102(X1,X2,X3)
U102(X1,mark(X2),X3) -> U102(X1,X2,X3)
U102(X1,X2,mark(X3)) -> U102(X1,X2,X3)
U102(active(X1),X2,X3) -> U102(X1,X2,X3)
U102(X1,active(X2),X3) -> U102(X1,X2,X3)
U102(X1,X2,active(X3)) -> U102(X1,X2,X3)
isNatKind(mark(X)) -> isNatKind(X)
isNatKind(active(X)) -> isNatKind(X)
U103(mark(X1),X2,X3) -> U103(X1,X2,X3)
U103(X1,mark(X2),X3) -> U103(X1,X2,X3)
U103(X1,X2,mark(X3)) -> U103(X1,X2,X3)
U103(active(X1),X2,X3) -> U103(X1,X2,X3)
U103(X1,active(X2),X3) -> U103(X1,X2,X3)
U103(X1,X2,active(X3)) -> U103(X1,X2,X3)
isNatIListKind(mark(X)) -> isNatIListKind(X)
isNatIListKind(active(X)) -> isNatIListKind(X)
U104(mark(X1),X2,X3) -> U104(X1,X2,X3)
U104(X1,mark(X2),X3) -> U104(X1,X2,X3)
U104(X1,X2,mark(X3)) -> U104(X1,X2,X3)
U104(active(X1),X2,X3) -> U104(X1,X2,X3)
U104(X1,active(X2),X3) -> U104(X1,X2,X3)
U104(X1,X2,active(X3)) -> U104(X1,X2,X3)
U105(mark(X1),X2) -> U105(X1,X2)
U105(X1,mark(X2)) -> U105(X1,X2)
U105(active(X1),X2) -> U105(X1,X2)
U105(X1,active(X2)) -> U105(X1,X2)
isNat(mark(X)) -> isNat(X)
isNat(active(X)) -> isNat(X)
U106(mark(X)) -> U106(X)
U106(active(X)) -> U106(X)
isNatIList(mark(X)) -> isNatIList(X)
isNatIList(active(X)) -> isNatIList(X)
U11(mark(X1),X2) -> U11(X1,X2)
U11(X1,mark(X2)) -> U11(X1,X2)
U11(active(X1),X2) -> U11(X1,X2)
U11(X1,active(X2)) -> U11(X1,X2)
U12(mark(X1),X2) -> U12(X1,X2)
U12(X1,mark(X2)) -> U12(X1,X2)
U12(active(X1),X2) -> U12(X1,X2)
U12(X1,active(X2)) -> U12(X1,X2)
U111(mark(X1),X2,X3) -> U111(X1,X2,X3)
U111(X1,mark(X2),X3) -> U111(X1,X2,X3)
U111(X1,X2,mark(X3)) -> U111(X1,X2,X3)
U111(active(X1),X2,X3) -> U111(X1,X2,X3)
U111(X1,active(X2),X3) -> U111(X1,X2,X3)
U111(X1,X2,active(X3)) -> U111(X1,X2,X3)
U112(mark(X1),X2,X3) -> U112(X1,X2,X3)
U112(X1,mark(X2),X3) -> U112(X1,X2,X3)
U112(X1,X2,mark(X3)) -> U112(X1,X2,X3)
U112(active(X1),X2,X3) -> U112(X1,X2,X3)
U112(X1,active(X2),X3) -> U112(X1,X2,X3)
U112(X1,X2,active(X3)) -> U112(X1,X2,X3)
U113(mark(X1),X2,X3) -> U113(X1,X2,X3)
U113(X1,mark(X2),X3) -> U113(X1,X2,X3)
U113(X1,X2,mark(X3)) -> U113(X1,X2,X3)
U113(active(X1),X2,X3) -> U113(X1,X2,X3)
U113(X1,active(X2),X3) -> U113(X1,X2,X3)
U113(X1,X2,active(X3)) -> U113(X1,X2,X3)
U114(mark(X1),X2) -> U114(X1,X2)
U114(X1,mark(X2)) -> U114(X1,X2)
U114(active(X1),X2) -> U114(X1,X2)
U114(X1,active(X2)) -> U114(X1,X2)
s(mark(X)) -> s(X)
s(active(X)) -> s(X)
length(mark(X)) -> length(X)
length(active(X)) -> length(X)
U13(mark(X)) -> U13(X)
U13(active(X)) -> U13(X)
isNatList(mark(X)) -> isNatList(X)
isNatList(active(X)) -> isNatList(X)
U121(mark(X1),X2) -> U121(X1,X2)
U121(X1,mark(X2)) -> U121(X1,X2)
U121(active(X1),X2) -> U121(X1,X2)
U121(X1,active(X2)) -> U121(X1,X2)
U122(mark(X)) -> U122(X)
U122(active(X)) -> U122(X)
U131(mark(X1),X2,X3,X4) -> U131(X1,X2,X3,X4)
U131(X1,mark(X2),X3,X4) -> U131(X1,X2,X3,X4)
U131(X1,X2,mark(X3),X4) -> U131(X1,X2,X3,X4)
U131(X1,X2,X3,mark(X4)) -> U131(X1,X2,X3,X4)
U131(active(X1),X2,X3,X4) -> U131(X1,X2,X3,X4)
U131(X1,active(X2),X3,X4) -> U131(X1,X2,X3,X4)
U131(X1,X2,active(X3),X4) -> U131(X1,X2,X3,X4)
U131(X1,X2,X3,active(X4)) -> U131(X1,X2,X3,X4)
U132(mark(X1),X2,X3,X4) -> U132(X1,X2,X3,X4)
U132(X1,mark(X2),X3,X4) -> U132(X1,X2,X3,X4)
U132(X1,X2,mark(X3),X4) -> U132(X1,X2,X3,X4)
U132(X1,X2,X3,mark(X4)) -> U132(X1,X2,X3,X4)
U132(active(X1),X2,X3,X4) -> U132(X1,X2,X3,X4)
U132(X1,active(X2),X3,X4) -> U132(X1,X2,X3,X4)
U132(X1,X2,active(X3),X4) -> U132(X1,X2,X3,X4)
U132(X1,X2,X3,active(X4)) -> U132(X1,X2,X3,X4)
U133(mark(X1),X2,X3,X4) -> U133(X1,X2,X3,X4)
U133(X1,mark(X2),X3,X4) -> U133(X1,X2,X3,X4)
U133(X1,X2,mark(X3),X4) -> U133(X1,X2,X3,X4)
U133(X1,X2,X3,mark(X4)) -> U133(X1,X2,X3,X4)
U133(active(X1),X2,X3,X4) -> U133(X1,X2,X3,X4)
U133(X1,active(X2),X3,X4) -> U133(X1,X2,X3,X4)
U133(X1,X2,active(X3),X4) -> U133(X1,X2,X3,X4)
U133(X1,X2,X3,active(X4)) -> U133(X1,X2,X3,X4)
U134(mark(X1),X2,X3,X4) -> U134(X1,X2,X3,X4)
U134(X1,mark(X2),X3,X4) -> U134(X1,X2,X3,X4)
U134(X1,X2,mark(X3),X4) -> U134(X1,X2,X3,X4)
U134(X1,X2,X3,mark(X4)) -> U134(X1,X2,X3,X4)
U134(active(X1),X2,X3,X4) -> U134(X1,X2,X3,X4)
U134(X1,active(X2),X3,X4) -> U134(X1,X2,X3,X4)
U134(X1,X2,active(X3),X4) -> U134(X1,X2,X3,X4)
U134(X1,X2,X3,active(X4)) -> U134(X1,X2,X3,X4)
U135(mark(X1),X2,X3,X4) -> U135(X1,X2,X3,X4)
U135(X1,mark(X2),X3,X4) -> U135(X1,X2,X3,X4)
U135(X1,X2,mark(X3),X4) -> U135(X1,X2,X3,X4)
U135(X1,X2,X3,mark(X4)) -> U135(X1,X2,X3,X4)
U135(active(X1),X2,X3,X4) -> U135(X1,X2,X3,X4)
U135(X1,active(X2),X3,X4) -> U135(X1,X2,X3,X4)
U135(X1,X2,active(X3),X4) -> U135(X1,X2,X3,X4)
U135(X1,X2,X3,active(X4)) -> U135(X1,X2,X3,X4)
U136(mark(X1),X2,X3,X4) -> U136(X1,X2,X3,X4)
U136(X1,mark(X2),X3,X4) -> U136(X1,X2,X3,X4)
U136(X1,X2,mark(X3),X4) -> U136(X1,X2,X3,X4)
U136(X1,X2,X3,mark(X4)) -> U136(X1,X2,X3,X4)
U136(active(X1),X2,X3,X4) -> U136(X1,X2,X3,X4)
U136(X1,active(X2),X3,X4) -> U136(X1,X2,X3,X4)
U136(X1,X2,active(X3),X4) -> U136(X1,X2,X3,X4)
U136(X1,X2,X3,active(X4)) -> U136(X1,X2,X3,X4)
take(mark(X1),X2) -> take(X1,X2)
take(X1,mark(X2)) -> take(X1,X2)
take(active(X1),X2) -> take(X1,X2)
take(X1,active(X2)) -> take(X1,X2)
U21(mark(X1),X2) -> U21(X1,X2)
U21(X1,mark(X2)) -> U21(X1,X2)
U21(active(X1),X2) -> U21(X1,X2)
U21(X1,active(X2)) -> U21(X1,X2)
U22(mark(X1),X2) -> U22(X1,X2)
U22(X1,mark(X2)) -> U22(X1,X2)
U22(active(X1),X2) -> U22(X1,X2)
U22(X1,active(X2)) -> U22(X1,X2)
U23(mark(X)) -> U23(X)
U23(active(X)) -> U23(X)
U31(mark(X1),X2) -> U31(X1,X2)
U31(X1,mark(X2)) -> U31(X1,X2)
U31(active(X1),X2) -> U31(X1,X2)
U31(X1,active(X2)) -> U31(X1,X2)
U32(mark(X1),X2) -> U32(X1,X2)
U32(X1,mark(X2)) -> U32(X1,X2)
U32(active(X1),X2) -> U32(X1,X2)
U32(X1,active(X2)) -> U32(X1,X2)
U33(mark(X)) -> U33(X)
U33(active(X)) -> U33(X)
U41(mark(X1),X2,X3) -> U41(X1,X2,X3)
U41(X1,mark(X2),X3) -> U41(X1,X2,X3)
U41(X1,X2,mark(X3)) -> U41(X1,X2,X3)
U41(active(X1),X2,X3) -> U41(X1,X2,X3)
U41(X1,active(X2),X3) -> U41(X1,X2,X3)
U41(X1,X2,active(X3)) -> U41(X1,X2,X3)
U42(mark(X1),X2,X3) -> U42(X1,X2,X3)
U42(X1,mark(X2),X3) -> U42(X1,X2,X3)
U42(X1,X2,mark(X3)) -> U42(X1,X2,X3)
U42(active(X1),X2,X3) -> U42(X1,X2,X3)
U42(X1,active(X2),X3) -> U42(X1,X2,X3)
U42(X1,X2,active(X3)) -> U42(X1,X2,X3)
U43(mark(X1),X2,X3) -> U43(X1,X2,X3)
U43(X1,mark(X2),X3) -> U43(X1,X2,X3)
U43(X1,X2,mark(X3)) -> U43(X1,X2,X3)
U43(active(X1),X2,X3) -> U43(X1,X2,X3)
U43(X1,active(X2),X3) -> U43(X1,X2,X3)
U43(X1,X2,active(X3)) -> U43(X1,X2,X3)
U44(mark(X1),X2,X3) -> U44(X1,X2,X3)
U44(X1,mark(X2),X3) -> U44(X1,X2,X3)
U44(X1,X2,mark(X3)) -> U44(X1,X2,X3)
U44(active(X1),X2,X3) -> U44(X1,X2,X3)
U44(X1,active(X2),X3) -> U44(X1,X2,X3)
U44(X1,X2,active(X3)) -> U44(X1,X2,X3)
U45(mark(X1),X2) -> U45(X1,X2)
U45(X1,mark(X2)) -> U45(X1,X2)
U45(active(X1),X2) -> U45(X1,X2)
U45(X1,active(X2)) -> U45(X1,X2)
U46(mark(X)) -> U46(X)
U46(active(X)) -> U46(X)
U51(mark(X1),X2) -> U51(X1,X2)
U51(X1,mark(X2)) -> U51(X1,X2)
U51(active(X1),X2) -> U51(X1,X2)
U51(X1,active(X2)) -> U51(X1,X2)
U52(mark(X)) -> U52(X)
U52(active(X)) -> U52(X)
U61(mark(X1),X2) -> U61(X1,X2)
U61(X1,mark(X2)) -> U61(X1,X2)
U61(active(X1),X2) -> U61(X1,X2)
U61(X1,active(X2)) -> U61(X1,X2)
U62(mark(X)) -> U62(X)
U62(active(X)) -> U62(X)
U71(mark(X)) -> U71(X)
U71(active(X)) -> U71(X)
U81(mark(X)) -> U81(X)
U81(active(X)) -> U81(X)
U91(mark(X1),X2,X3) -> U91(X1,X2,X3)
U91(X1,mark(X2),X3) -> U91(X1,X2,X3)
U91(X1,X2,mark(X3)) -> U91(X1,X2,X3)
U91(active(X1),X2,X3) -> U91(X1,X2,X3)
U91(X1,active(X2),X3) -> U91(X1,X2,X3)
U91(X1,X2,active(X3)) -> U91(X1,X2,X3)
U92(mark(X1),X2,X3) -> U92(X1,X2,X3)
U92(X1,mark(X2),X3) -> U92(X1,X2,X3)
U92(X1,X2,mark(X3)) -> U92(X1,X2,X3)
U92(active(X1),X2,X3) -> U92(X1,X2,X3)
U92(X1,active(X2),X3) -> U92(X1,X2,X3)
U92(X1,X2,active(X3)) -> U92(X1,X2,X3)
U93(mark(X1),X2,X3) -> U93(X1,X2,X3)
U93(X1,mark(X2),X3) -> U93(X1,X2,X3)
U93(X1,X2,mark(X3)) -> U93(X1,X2,X3)
U93(active(X1),X2,X3) -> U93(X1,X2,X3)
U93(X1,active(X2),X3) -> U93(X1,X2,X3)
U93(X1,X2,active(X3)) -> U93(X1,X2,X3)
U94(mark(X1),X2,X3) -> U94(X1,X2,X3)
U94(X1,mark(X2),X3) -> U94(X1,X2,X3)
U94(X1,X2,mark(X3)) -> U94(X1,X2,X3)
U94(active(X1),X2,X3) -> U94(X1,X2,X3)
U94(X1,active(X2),X3) -> U94(X1,X2,X3)
U94(X1,X2,active(X3)) -> U94(X1,X2,X3)
U95(mark(X1),X2) -> U95(X1,X2)
U95(X1,mark(X2)) -> U95(X1,X2)
U95(active(X1),X2) -> U95(X1,X2)
U95(X1,active(X2)) -> U95(X1,X2)
U96(mark(X)) -> U96(X)
U96(active(X)) -> U96(X)
)