ceta_eq: termination proof not accepted
1: error below switch to dependency pairs
1.1: error below the dependency graph 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 reduction pair 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 reduction pair processor
       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: error below the reduction pair 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#(fst(X1, X2)) -> mark#(X1)
           mark#(fst(X1, X2)) -> mark#(X2)
           rules:
           
           active(fst(0, Z)) -> mark(nil)
           active(fst(s(X), cons(Y, Z))) -> mark(cons(Y, fst(X, Z)))
           active(from(X)) -> mark(cons(X, from(s(X))))
           active(add(0, X)) -> mark(X)
           active(add(s(X), Y)) -> mark(s(add(X, Y)))
           active(len(nil)) -> mark(0)
           active(len(cons(X, Z))) -> mark(s(len(Z)))
           add(mark(X1), X2) -> add(X1, X2)
           add(X1, mark(X2)) -> add(X1, X2)
           add(active(X1), X2) -> add(X1, X2)
           add(X1, active(X2)) -> add(X1, X2)
           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)
           from(mark(X)) -> from(X)
           from(active(X)) -> from(X)
           fst(mark(X1), X2) -> fst(X1, X2)
           fst(X1, mark(X2)) -> fst(X1, X2)
           fst(active(X1), X2) -> fst(X1, X2)
           fst(X1, active(X2)) -> fst(X1, X2)
           len(mark(X)) -> len(X)
           len(active(X)) -> len(X)
           mark(fst(X1, X2)) -> active(fst(mark(X1), mark(X2)))
           mark(0) -> active(0)
           mark(nil) -> active(nil)
           mark(s(X)) -> active(s(X))
           mark(cons(X1, X2)) -> active(cons(mark(X1), X2))
           mark(from(X)) -> active(from(mark(X)))
           mark(add(X1, X2)) -> active(add(mark(X1), mark(X2)))
           mark(len(X)) -> active(len(mark(X)))
           s(mark(X)) -> s(X)
           s(active(X)) -> s(X)
           
            the pairs 
           mark#(fst(X1, X2)) -> mark#(X1)
           mark#(fst(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(fst(x_1, x_2)) = 1 + x_2 + x_1
           problem when orienting DPs
           cannot orient pair mark#(fst(X1, X2)) -> mark#(X1) strictly:
           [(mark#(fst(X1, X2)),0),(fst(X1, X2),0)] >mu [(mark#(X1),0),(X1,0)] could not be ensured