MAYBE
* Step 1: Failure MAYBE
  + Considered Problem:
      - Strict TRS:
          ack_in(0(),n) -> ack_out(s(n))
          ack_in(s(m),0()) -> u11(ack_in(m,s(0())))
          ack_in(s(m),s(n)) -> u21(ack_in(s(m),n),m)
          u11(ack_out(n)) -> ack_out(n)
          u21(ack_out(n),m) -> u22(ack_in(m,n))
          u22(ack_out(n)) -> ack_out(n)
      - Signature:
          {ack_in/2,u11/1,u21/2,u22/1} / {0/0,ack_out/1,s/1}
      - Obligation:
          innermost runtime complexity wrt. defined symbols {ack_in,u11,u21,u22} and constructors {0,ack_out,s}
  + Applied Processor:
      Ara {heuristics_ = NoHeuristics, minDegree = 1, maxDegree = 3, araTimeout = 60, araFindStrictRules = Nothing, araSmtSolver = MiniSMT}
  + Details:
      The input can not be schown compatible.
MAYBE