YES
exiting with thread!
(VAR x )
(RULES 
        a(a(x)) -> d(c(x))
        c(c(x)) -> b(x)
        b(a(c(x))) -> d(d(x))
        a(d(c(x))) -> d(c(a(x)))
        c(d(x)) -> d(c(x))
        b(c(x)) -> b(b(x))
        d(b(x)) -> b(d(x))
        c(b(x)) -> b(b(x))
        a(b(x)) -> b(b(x))
        b(b(b(x))) -> b(b(x))
        b(b(d(x))) -> b(b(x))
        d(d(c(x))) -> b(b(x))
        b(d(d(x))) -> b(b(x))
        b(d(c(x))) -> b(b(x))
        a(d(d(x))) -> b(b(x))
        d(c(a(c(x)))) -> b(b(x))
        d(c(a(d(x)))) -> b(b(x))
        d(d(d(x))) -> b(b(x))
        b(b(a(x))) -> b(b(x))
        b(d(a(c(x)))) -> b(b(x))
        b(d(a(d(x)))) -> b(b(x))
        
)