YES(?,ELEMENTARY)

'epo* (timeout of 60.0 seconds)'
--------------------------------
Answer:           YES(?,ELEMENTARY)
Input Problem:    innermost runtime-complexity with respect to
  Rules:
    {  app(nil(), xs) -> nil()
     , app(cons(x, xs), ys) -> cons(x, app(xs, ys))}

Proof Output:    
  Strict Rules in Predicative Notation:
   {  app(nil(); xs) -> nil()
    , app(cons(; x, xs); ys) -> cons(; x, app(xs; ys))}
  Safe Mapping:
   safe(app) = {2}, safe(nil) = {}, safe(cons) = {1, 2}
  Argument Permutation:
   mu(app) = [1, 2]
  Precedence:
   app ~ app