(VAR x1 )
(RULES 
        q0(a(x1)) -> x(q1(x1))
        q1(a(x1)) -> a(q1(x1))
        q1(y(x1)) -> y(q1(x1))
        a(q1(b(x1))) -> q2(a(y(x1)))
        a(q2(a(x1))) -> q2(a(a(x1)))
        a(q2(y(x1))) -> q2(a(y(x1)))
        y(q1(b(x1))) -> q2(y(y(x1)))
        y(q2(a(x1))) -> q2(y(a(x1)))
        y(q2(y(x1))) -> q2(y(y(x1)))
        q2(x(x1)) -> x(q0(x1))
        q0(y(x1)) -> y(q3(x1))
        q3(y(x1)) -> y(q3(x1))
        q3(bl(x1)) -> bl(q4(x1))
        
)