(VAR x)
(RULES
  a -> a
  a -> b
  f(b,b) -> f(a,b)
  f(x,a) -> f(a,b)
)
(COMMENT
generated by FORT -f "a:0 b:0 f:2" -r 4 "UN & ~UNC & ~SN"
submitted by: Franziska Rapp
)