YES(?,ELEMENTARY)

'epo* (timeout of 60.0 seconds)'
--------------------------------
Answer:           YES(?,ELEMENTARY)
Input Problem:    innermost runtime-complexity with respect to
  Rules:
    {  plus(x, 0()) -> x
     , plus(x, s(y)) -> s(plus(x, y))
     , double(x) -> plus(x, x)}

Proof Output:    
  Strict Rules in Predicative Notation:
   {  plus(0(); x) -> x
    , plus(s(; y); x) -> s(; plus(y; x))
    , double(x;) -> plus(x; x)}
  Safe Mapping:
   safe(plus) = {1}, safe(0) = {}, safe(s) = {1}, safe(double) = {}
  Argument Permutation:
   mu(plus) = [1, 2], mu(double) = [1]
  Precedence:
   double ~ double, double > plus, plus ~ plus