YES
(VAR x)
(RULES
c(d(x)) -> a(a(x))
d(c(x)) -> a(a(x))
d(a(a(x))) -> c(c(c(x)))
c(c(c(a(x)))) -> c(c(c(x)))
a(a(d(x))) -> c(c(c(x)))
c(c(a(a(x)))) -> c(c(c(x)))
a(c(a(a(x)))) -> c(c(c(x)))
a(a(a(a(x)))) -> c(c(c(x)))
d(d(x)) -> c(c(a(c(x))))
c(c(c(c(x)))) -> c(c(c(x)))
a(c(c(x))) -> c(c(c(x)))
a(a(c(x))) -> c(a(a(x)))
b(x) -> c(c(x))
)