ceta_eq: termination proof not accepted
1: error below switch to dependency pairs
1.1: error below the dependency graph processor
 1.1.2: error below the reduction pair processor
  1.1.2.1: error when applying the reduction pair processor with usable rules to remove from the DP problem
   pairs:
   
   active#(2nd(X)) -> active#(X)
   active#(from(X)) -> active#(X)
   active#(s(X)) -> active#(X)
   rules:
   
   2nd(mark(X)) -> mark(2nd(X))
   2nd(ok(X)) -> ok(2nd(X))
   active(2nd(cons(X, cons(Y, Z)))) -> mark(Y)
   active(from(X)) -> mark(cons(X, from(s(X))))
   active(2nd(X)) -> 2nd(active(X))
   active(cons(X1, X2)) -> cons(active(X1), X2)
   active(from(X)) -> from(active(X))
   active(s(X)) -> s(active(X))
   cons(mark(X1), X2) -> mark(cons(X1, X2))
   cons(ok(X1), ok(X2)) -> ok(cons(X1, X2))
   from(mark(X)) -> mark(from(X))
   from(ok(X)) -> ok(from(X))
   proper(2nd(X)) -> 2nd(proper(X))
   proper(cons(X1, X2)) -> cons(proper(X1), proper(X2))
   proper(from(X)) -> from(proper(X))
   proper(s(X)) -> s(proper(X))
   s(mark(X)) -> mark(s(X))
   s(ok(X)) -> ok(s(X))
   top(mark(X)) -> top(proper(X))
   top(ok(X)) -> top(active(X))
   
    the pairs 
   active#(from(X)) -> active#(X)
   
   could not apply the generic root reduction pair processor with the following
   SCNP-version with mu = MS and the level mapping defined by 
   pi(active#) = [(epsilon,0),(1,0)]
   Argument Filter: 
   pi(active#/1) = []
   pi(2nd/1) = 1
   pi(from/1) = [1]
   pi(s/1) = 1
   
   RPO with the following precedence
   precedence(active#[1]) = 0
   precedence(from[1]) = 1
   
   precedence(_) = 0
   and the following status
   status(active#[1]) = lex
   status(from[1]) = lex
   
   status(_) = lex
   
   problem when orienting DPs
   cannot orient pair active#(2nd(X)) -> active#(X) weakly:
   [(active#(2nd(X)),0),(2nd(X),0)] >=mu [(active#(X),0),(X,0)] could not be ensured