YES(?,ELEMENTARY)

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

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