(VAR s x )
(STRATEGY OUTERMOST)
(RULES 
        M -> h(cons(0, tail(M)))
        tail(cons(x, s)) -> s
        h(cons(0, s)) -> cons(0, cons(1, h(s)))
        h(cons(1, s)) -> cons(1, cons(0, h(s)))
        cons(x, s) -> garbage
        
)