MAYBE

(format LCTRS)
(fun a 0 :sort (Unit))
(fun b 0 :sort (Unit))
(fun c 0 :sort (Unit))
(fun d 0 :sort (Unit))
(fun f 4 :sort (Unit Unit Unit Unit Unit))

(rule (f a a b b) (f c c c c))
(rule a b)
(rule a c)
(rule b a)
(rule b c)

Confluence could not be determined.

Elapsed Time:  62.13 ms