MAYBE
Input TRS:
      1: a(c(x1)) -> c(b(c(c(a(x1)))))
      2: b(b(b(x1))) -> c(b(x1))
      3: d(d(x1)) -> d(b(d(b(d(x1)))))
      4: a(a(x1)) -> a(d(a(x1)))
      5: a(b(x1)) -> c(c(a(x1)))
      6: c(c(x1)) -> c(b(c(b(c(x1)))))
      7: c(c(c(x1))) -> c(b(b(x1)))
Number of strict rules: 7
Direct POLO(bPol) ... failed.
Uncurrying ... failed.
Dependency Pairs:
     #1: #b(b(b(x1))) -> #c(b(x1))
     #2: #c(c(x1)) -> #c(b(c(b(c(x1)))))
     #3: #c(c(x1)) -> #b(c(b(c(x1))))
     #4: #c(c(x1)) -> #c(b(c(x1)))
     #5: #c(c(x1)) -> #b(c(x1))
     #6: #c(c(c(x1))) -> #c(b(b(x1)))
     #7: #c(c(c(x1))) -> #b(b(x1))
     #8: #c(c(c(x1))) -> #b(x1)
     #9: #a(b(x1)) -> #c(c(a(x1)))
     #10: #a(b(x1)) -> #c(a(x1))
     #11: #a(b(x1)) -> #a(x1)
     #12: #d(d(x1)) -> #d(b(d(b(d(x1)))))
     #13: #d(d(x1)) -> #b(d(b(d(x1))))
     #14: #d(d(x1)) -> #d(b(d(x1)))
     #15: #d(d(x1)) -> #b(d(x1))
     #16: #a(c(x1)) -> #c(b(c(c(a(x1)))))
     #17: #a(c(x1)) -> #b(c(c(a(x1))))
     #18: #a(c(x1)) -> #c(c(a(x1)))
     #19: #a(c(x1)) -> #c(a(x1))
     #20: #a(c(x1)) -> #a(x1)
     #21: #a(a(x1)) -> #a(d(a(x1)))
     #22: #a(a(x1)) -> #d(a(x1))
Number of SCCs: 2, DPs: 6
  SCC { #11 #20 }
POLO(Sum)... succeeded.
      a 	w: 0
      d 	w: 0
      b 	w: x1 + 1
      c 	w: x1 + 1
      #d 	w: 0
      #c 	w: 0
      #a 	w: x1
      #b 	w: 0
    USABLE RULES: { }
    Removed DPs: #11 #20
Number of SCCs: 1, DPs: 4
  SCC { #1 #6..8 }
POLO(Sum)... POLO(max)... QLPOS... POLO(mSum)... QWPOpS(mSum)... Mat2b... failed.
Finding a loop...  failed.