MAYBE
MAYBE
TRS:
 {
  u21(ackout(X), Y) -> u22(ackin(Y, X)),
  ackin(s(X), s(Y)) -> u21(ackin(s(X), Y), X)
 }
 DUP: We consider a duplicating system.
  Trs:
   {
    u21(ackout(X), Y) -> u22(ackin(Y, X)),
    ackin(s(X), s(Y)) -> u21(ackin(s(X), Y), X)
   }
  Fail