(VAR x y)
(RULES
  f(u(O), u(y)) -> A
  f(v(x), v(O)) -> B
  O -> u(O)
  O -> v(O)
  u(x) -> x
  v(x) -> x
  f(x, y) -> f(x, u(y))
  f(x, y) -> f(v(x), y)
)
(COMMENT
  Example 4 from [F12-IWC]. not confluent.
)