YES(?,ELEMENTARY)

'epo* (timeout of 60.0 seconds)'
--------------------------------
Answer:           YES(?,ELEMENTARY)
Input Problem:    innermost runtime-complexity with respect to
  Rules:
    {  rev(a()) -> a()
     , rev(b()) -> b()
     , rev(++(x, y)) -> ++(rev(y), rev(x))
     , rev(++(x, x)) -> rev(x)}

Proof Output:    
  Strict Rules in Predicative Notation:
   {  rev(a();) -> a()
    , rev(b();) -> b()
    , rev(++(; x, y);) -> ++(; rev(y;), rev(x;))
    , rev(++(; x, x);) -> rev(x;)}
  Safe Mapping:
   safe(rev) = {}, safe(a) = {}, safe(b) = {}, safe(++) = {1, 2}
  Argument Permutation:
   mu(rev) = [1]
  Precedence:
   rev ~ rev