YES

TRS:

  a__zeros() -> cons(0(),zeros())
  a__U11(tt()) -> tt()
  a__U21(tt()) -> tt()
  a__U31(tt()) -> tt()
  a__U41(tt(),V2) -> a__U42(a__isNatIList(V2))
  a__U42(tt()) -> tt()
  a__U51(tt(),V2) -> a__U52(a__isNatList(V2))
  a__U52(tt()) -> tt()
  a__U61(tt(),L,N) -> a__U62(a__isNat(N),L)
  a__U62(tt(),L) -> s(a__length(mark(L)))
  a__isNat(0()) -> tt()
  a__isNat(length(V1)) -> a__U11(a__isNatList(V1))
  a__isNat(s(V1)) -> a__U21(a__isNat(V1))
  a__isNatIList(V) -> a__U31(a__isNatList(V))
  a__isNatIList(zeros()) -> tt()
  a__isNatIList(cons(V1,V2)) -> a__U41(a__isNat(V1),V2)
  a__isNatList(nil()) -> tt()
  a__isNatList(cons(V1,V2)) -> a__U51(a__isNat(V1),V2)
  a__length(nil()) -> 0()
  a__length(cons(N,L)) -> a__U61(a__isNatList(L),L,N)
  mark(zeros()) -> a__zeros()
  mark(U11(X)) -> a__U11(mark(X))
  mark(U21(X)) -> a__U21(mark(X))
  mark(U31(X)) -> a__U31(mark(X))
  mark(U41(X1,X2)) -> a__U41(mark(X1),X2)
  mark(U42(X)) -> a__U42(mark(X))
  mark(isNatIList(X)) -> a__isNatIList(X)
  mark(U51(X1,X2)) -> a__U51(mark(X1),X2)
  mark(U52(X)) -> a__U52(mark(X))
  mark(isNatList(X)) -> a__isNatList(X)
  mark(U61(X1,X2,X3)) -> a__U61(mark(X1),X2,X3)
  mark(U62(X1,X2)) -> a__U62(mark(X1),X2)
  mark(isNat(X)) -> a__isNat(X)
  mark(length(X)) -> a__length(mark(X))
  mark(cons(X1,X2)) -> cons(mark(X1),X2)
  mark(0()) -> 0()
  mark(tt()) -> tt()
  mark(s(X)) -> s(mark(X))
  mark(nil()) -> nil()
  a__zeros() -> zeros()
  a__U11(X) -> U11(X)
  a__U21(X) -> U21(X)
  a__U31(X) -> U31(X)
  a__U41(X1,X2) -> U41(X1,X2)
  a__U42(X) -> U42(X)
  a__isNatIList(X) -> isNatIList(X)
  a__U51(X1,X2) -> U51(X1,X2)
  a__U52(X) -> U52(X)
  a__isNatList(X) -> isNatList(X)
  a__U61(X1,X2,X3) -> U61(X1,X2,X3)
  a__U62(X1,X2) -> U62(X1,X2)
  a__isNat(X) -> isNat(X)
  a__length(X) -> length(X)

max/plus interpretations on N:

  a__zeros_A = 495
  a__zeros#_A = 686
  cons_A(x1,x2) = max{12, 320 + x1, 469 + x2}
  cons#_A(x1,x2) = max{685, 660, 674}
  0_A = 175
  0#_A = 682
  zeros_A = 26
  zeros#_A = 683
  a__U11_A(x1) = max{669, x1}
  a__U11#_A(x1) = max{678, 678}
  tt_A = 670
  tt#_A = 682
  a__U21_A(x1) = max{670, x1}
  a__U21#_A(x1) = max{324, -346 + x1}
  a__U31_A(x1) = max{670, 7 + x1}
  a__U31#_A(x1) = max{667, 671}
  a__U41_A(x1,x2) = max{374, 13 + x1, 684 + x2}
  a__U41#_A(x1,x2) = max{684, 682, 680 + x2}
  a__U42_A(x1) = max{684, x1}
  a__U42#_A(x1) = max{681, 683}
  a__isNatIList_A(x1) = max{684, 362 + x1}
  a__isNatIList#_A(x1) = max{679, 666 + x1}
  a__U51_A(x1,x2) = max{623, 101 + x1, 668 + x2}
  a__U51#_A(x1,x2) = max{666, 659, 663}
  a__U52_A(x1) = max{669, 266 + x1}
  a__U52#_A(x1) = max{656, 658}
  a__isNatList_A(x1) = max{402, 302 + x1}
  a__isNatList#_A(x1) = max{665, 664}
  a__U61_A(x1,x2,x3) = max{321, 116 + x1, 365 + x2, 320 + x3}
  a__U61#_A(x1,x2,x3) = max{673, 284 + x1, 678 + x2, 632 + x3}
  a__U62_A(x1,x2) = max{366, 18 + x1, 365 + x2}
  a__U62#_A(x1,x2) = max{667, 174 + x1, 671 + x2}
  a__isNat_A(x1) = max{670, 302 + x1}
  a__isNat#_A(x1) = max{678, 678}
  s_A(x1) = max{367, 19 + x1}
  s#_A(x1) = max{679, 325 + x1}
  a__length_A(x1) = max{518, x1}
  a__length#_A(x1) = max{666, 313 + x1}
  mark_A(x1) = max{495, 346 + x1}
  mark#_A(x1) = max{672, 661 + x1}
  length_A(x1) = max{172, x1}
  length#_A(x1) = max{665, 660}
  nil_A = 496
  nil#_A = 1158
  U11_A(x1) = max{323, x1}
  U11#_A(x1) = max{671, 678}
  U21_A(x1) = max{324, x1}
  U21#_A(x1) = max{0, -347}
  U31_A(x1) = max{324, 7 + x1}
  U31#_A(x1) = max{668, 662}
  U41_A(x1,x2) = max{12, 13 + x1, 338 + x2}
  U41#_A(x1,x2) = max{671, 683, 680 + x2}
  U42_A(x1) = max{338, x1}
  U42#_A(x1) = max{682, 681}
  isNatIList_A(x1) = max{363, 17 + x1}
  isNatIList#_A(x1) = max{0, 665}
  U51_A(x1,x2) = max{0, 101 + x1, 624 + x2}
  U51#_A(x1,x2) = max{663, 662, 662}
  U52_A(x1) = max{415, 266 + x1}
  U52#_A(x1) = max{657, 657}
  isNatList_A(x1) = max{0, 5 + x1}
  isNatList#_A(x1) = max{0, 663}
  U61_A(x1,x2,x3) = max{0, 116 + x1, 322 + x2, 117 + x3}
  U61#_A(x1,x2,x3) = max{660, 631, 283 + x2, 283}
  U62_A(x1,x2) = max{9, 18 + x1, 365 + x2}
  U62#_A(x1,x2) = max{668, 173, 670}
  isNat_A(x1) = max{324, 302 + x1}
  isNat#_A(x1) = max{678, 677}

precedence:

  a__zeros > 0 > cons = a__length = nil = U61 > zeros = tt = a__U61 > a__U62 = U52 > a__U41 = mark > a__U42 = s = U41 = U62 > a__isNat = U21 = U42 > a__U21 = a__isNatIList > a__U31 = a__isNatList = length > a__U11 = a__U51 = U31 = isNatList > a__U52 = U11 = isNatIList = U51 = isNat