MAYBE

Problem:
 r1(a(x1)) -> a(a(a(r1(x1))))
 r2(a(x1)) -> a(a(a(r2(x1))))
 a(l1(x1)) -> l1(a(a(a(x1))))
 a(a(l2(x1))) -> l2(a(a(x1)))
 r1(b(x1)) -> l1(b(x1))
 r2(b(x1)) -> l2(a(b(x1)))
 b(l1(x1)) -> b(r2(x1))
 b(l2(x1)) -> b(r1(x1))
 a(a(x1)) -> x1

Proof:
 Open