MAYBE
Input TRS:
      1: a(x1) -> b(b(x1))
      2: c(b(x1)) -> d(x1)
      3: e(b(x1)) -> c(c(x1))
      4: d(b(x1)) -> b(f(x1))
      5: f(x1) -> a(e(x1))
      6: c(x1) -> x1
      7: a(a(x1)) -> f(x1)
Number of strict rules: 7
Direct POLO(bPol) ... failed.
Uncurrying ... failed.
Dependency Pairs:
     #1: #c(b(x1)) -> #d(x1)
     #2: #a(a(x1)) -> #f(x1)
     #3: #f(x1) -> #a(e(x1))
     #4: #f(x1) -> #e(x1)
     #5: #e(b(x1)) -> #c(c(x1))
     #6: #e(b(x1)) -> #c(x1)
     #7: #d(b(x1)) -> #f(x1)
Number of SCCs: 1, DPs: 7
  SCC { #1..7 }
POLO(Sum)... POLO(max)... QLPOS... POLO(mSum)... QWPOpS(mSum)... Mat2b... failed.
Finding a loop...  failed.