(VAR x y )
(RULES
f(x,a(a(b(b(y))))) -> f(a(a(a(b(b(b(x)))))),y)
f(a(x),y) -> f(x,a(y))
f(b(x),y) -> f(x,b(y))
)
(COMMENT TRS variant of aabb -> bbbaaa )