ceta_eq: termination proof not accepted
1: error below switch to dependency pairs
1.1: error below the reduction pair processor
 1.1.1: error below the reduction pair processor
  1.1.1.1: error below the reduction pair processor
   1.1.1.1.1: error below the dependency graph processor
    1.1.1.1.1.1: error below the reduction pair processor
     1.1.1.1.1.1.1: error below the reduction pair processor
      1.1.1.1.1.1.1.1: error below the dependency graph processor
       1.1.1.1.1.1.1.1.1: error below the reduction pair processor
        1.1.1.1.1.1.1.1.1.1: error below the dependency graph processor
         1.1.1.1.1.1.1.1.1.1.1: error below the reduction pair processor
          1.1.1.1.1.1.1.1.1.1.1.1: error when applying the reduction pair processor with usable rules to remove from the DP problem
           pairs:
           
           mark#(plus(X1, X2)) -> mark#(X1)
           mark#(plus(X1, X2)) -> mark#(X2)
           rules:
           
           a__U11(tt, N) -> mark(N)
           a__U11(X1, X2) -> U11(X1, X2)
           a__U21(tt, M, N) -> s(a__plus(mark(N), mark(M)))
           a__U21(X1, X2, X3) -> U21(X1, X2, X3)
           a__and(tt, X) -> mark(X)
           a__and(X1, X2) -> and(X1, X2)
           a__isNat(0) -> tt
           a__isNat(plus(V1, V2)) -> a__and(a__isNat(V1), isNat(V2))
           a__isNat(s(V1)) -> a__isNat(V1)
           a__isNat(X) -> isNat(X)
           a__plus(N, 0) -> a__U11(a__isNat(N), N)
           a__plus(N, s(M)) -> a__U21(a__and(a__isNat(M), isNat(N)), M, N)
           a__plus(X1, X2) -> plus(X1, X2)
           mark(U11(X1, X2)) -> a__U11(mark(X1), X2)
           mark(U21(X1, X2, X3)) -> a__U21(mark(X1), X2, X3)
           mark(plus(X1, X2)) -> a__plus(mark(X1), mark(X2))
           mark(and(X1, X2)) -> a__and(mark(X1), X2)
           mark(isNat(X)) -> a__isNat(X)
           mark(tt) -> tt
           mark(s(X)) -> s(mark(X))
           mark(0) -> 0
           
            the pairs 
           mark#(plus(X1, X2)) -> mark#(X1)
           mark#(plus(X1, X2)) -> mark#(X2)
           
           could not apply the generic root reduction pair processor with the following
           SCNP-version with mu = MS and the level mapping defined by 
           pi(mark#) = [(epsilon,0),(1,0)]
           polynomial interpretration over naturals with negative constants
           Pol(mark#(x_1)) = 1
           Pol(plus(x_1, x_2)) = 1 + x_2 + x_1
           problem when orienting DPs
           cannot orient pair mark#(plus(X1, X2)) -> mark#(X1) strictly:
           [(mark#(plus(X1, X2)),0),(plus(X1, X2),0)] >mu [(mark#(X1),0),(X1,0)] could not be ensured