(VAR x)
(RULES
  c0 -> c0
  c0 -> c1
  f0(c1, c1) -> f0(c0, c1)
  f0(x, c0) -> f0(c0, c1)
)
(COMMENT -f "a:0 b:0 f:2" -r 4 "UN & ~UNC & ~SN")