MAYBE

Problem:
 strict:
  a(a(b(b(a(a(x1)))))) -> a(a(b(b(b(b(a(a(x1))))))))
  b(b(a(a(b(b(x1)))))) -> b(b(a(a(a(a(b(b(x1))))))))
 weak:
  a(a(x1)) -> a(a(a(a(a(a(x1))))))
  b(b(x1)) -> b(b(b(b(b(b(x1))))))

Proof:
 Open