(VAR x)
(RULES
  c1 -> c0
  c1 -> c2
  c2 -> c2
  c3 -> c2
  c3 -> c4
  f0(x, c0) -> c5
  f0(x, c4) -> c5
  f0(x, c5) -> c5  
  f0(c2, x) -> c5
)
(COMMENT p.30 of \cite{IWC16}
  GUN & ~UN & ~GUNC
)