MAYBE
TRS:
 {   a__f(X1, X2, X3) -> f(X1, X2, X3),
    a__f(a(), b(), X) -> a__f(X, X, mark(X)),
            mark(a()) -> a(),
            mark(b()) -> b(),
  mark(f(X1, X2, X3)) -> a__f(X1, X2, mark(X3)),
            mark(c()) -> a__c(),
               a__c() -> a(),
               a__c() -> b(),
               a__c() -> c()}
 DP:
  Strict:
   {  a__f#(a(), b(), X) -> a__f#(X, X, mark(X)),
      a__f#(a(), b(), X) -> mark#(X),
    mark#(f(X1, X2, X3)) -> a__f#(X1, X2, mark(X3)),
    mark#(f(X1, X2, X3)) -> mark#(X3),
              mark#(c()) -> a__c#()}
  Weak:
  {   a__f(X1, X2, X3) -> f(X1, X2, X3),
     a__f(a(), b(), X) -> a__f(X, X, mark(X)),
             mark(a()) -> a(),
             mark(b()) -> b(),
   mark(f(X1, X2, X3)) -> a__f(X1, X2, mark(X3)),
             mark(c()) -> a__c(),
                a__c() -> a(),
                a__c() -> b(),
                a__c() -> c()}
  EDG:
   {(a__f#(a(), b(), X) -> a__f#(X, X, mark(X)), a__f#(a(), b(), X) -> mark#(X))
    (a__f#(a(), b(), X) -> a__f#(X, X, mark(X)), a__f#(a(), b(), X) -> a__f#(X, X, mark(X)))
    (mark#(f(X1, X2, X3)) -> mark#(X3), mark#(c()) -> a__c#())
    (mark#(f(X1, X2, X3)) -> mark#(X3), mark#(f(X1, X2, X3)) -> mark#(X3))
    (mark#(f(X1, X2, X3)) -> mark#(X3), mark#(f(X1, X2, X3)) -> a__f#(X1, X2, mark(X3)))
    (mark#(f(X1, X2, X3)) -> a__f#(X1, X2, mark(X3)), a__f#(a(), b(), X) -> a__f#(X, X, mark(X)))
    (mark#(f(X1, X2, X3)) -> a__f#(X1, X2, mark(X3)), a__f#(a(), b(), X) -> mark#(X))
    (a__f#(a(), b(), X) -> mark#(X), mark#(f(X1, X2, X3)) -> a__f#(X1, X2, mark(X3)))
    (a__f#(a(), b(), X) -> mark#(X), mark#(f(X1, X2, X3)) -> mark#(X3))
    (a__f#(a(), b(), X) -> mark#(X), mark#(c()) -> a__c#())}
   SCCS:
    Scc:
     {  a__f#(a(), b(), X) -> a__f#(X, X, mark(X)),
        a__f#(a(), b(), X) -> mark#(X),
      mark#(f(X1, X2, X3)) -> a__f#(X1, X2, mark(X3)),
      mark#(f(X1, X2, X3)) -> mark#(X3)}
    SCC:
     Strict:
      {  a__f#(a(), b(), X) -> a__f#(X, X, mark(X)),
         a__f#(a(), b(), X) -> mark#(X),
       mark#(f(X1, X2, X3)) -> a__f#(X1, X2, mark(X3)),
       mark#(f(X1, X2, X3)) -> mark#(X3)}
     Weak:
     {   a__f(X1, X2, X3) -> f(X1, X2, X3),
        a__f(a(), b(), X) -> a__f(X, X, mark(X)),
                mark(a()) -> a(),
                mark(b()) -> b(),
      mark(f(X1, X2, X3)) -> a__f(X1, X2, mark(X3)),
                mark(c()) -> a__c(),
                   a__c() -> a(),
                   a__c() -> b(),
                   a__c() -> c()}
     POLY:
      Argument Filtering:
       pi(c) = [], pi(f) = [2], pi(a__c) = [], pi(b) = [], pi(a) = [], pi(mark#) = [0], pi(mark) = 0, pi(a__f#) = [2], pi(a__f) = [2]
      Usable Rules:
       {}
      Interpretation:
       [a__f#](x0) = x0 + 1,
       [mark#](x0) = x0 + 1,
       [f](x0) = x0 + 1
      Strict:
       {a__f#(a(), b(), X) -> a__f#(X, X, mark(X)),
        a__f#(a(), b(), X) -> mark#(X)}
      Weak:
       {   a__f(X1, X2, X3) -> f(X1, X2, X3),
          a__f(a(), b(), X) -> a__f(X, X, mark(X)),
                  mark(a()) -> a(),
                  mark(b()) -> b(),
        mark(f(X1, X2, X3)) -> a__f(X1, X2, mark(X3)),
                  mark(c()) -> a__c(),
                     a__c() -> a(),
                     a__c() -> b(),
                     a__c() -> c()}
      EDG:
       {(a__f#(a(), b(), X) -> a__f#(X, X, mark(X)), a__f#(a(), b(), X) -> mark#(X))
        (a__f#(a(), b(), X) -> a__f#(X, X, mark(X)), a__f#(a(), b(), X) -> a__f#(X, X, mark(X)))}
       SCCS:
        Scc:
         {a__f#(a(), b(), X) -> a__f#(X, X, mark(X))}
        SCC:
         Strict:
          {a__f#(a(), b(), X) -> a__f#(X, X, mark(X))}
         Weak:
         {   a__f(X1, X2, X3) -> f(X1, X2, X3),
            a__f(a(), b(), X) -> a__f(X, X, mark(X)),
                    mark(a()) -> a(),
                    mark(b()) -> b(),
          mark(f(X1, X2, X3)) -> a__f(X1, X2, mark(X3)),
                    mark(c()) -> a__c(),
                       a__c() -> a(),
                       a__c() -> b(),
                       a__c() -> c()}
         Fail