YES(?,ELEMENTARY)

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

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