(VAR x y z)
(THEORY (AC plus times))
(RULES
  plus(x, 0) -> x
  plus(x, s(y)) -> s(plus(x, y))
  times(x, 0) -> 0
  times(x, s(y)) -> plus(times(x, y), x)
  times(x, plus(y, z)) -> plus(times(x, y), times(x, z))
)