(STRATEGY
    INNERMOST)

(VAR
    x1)
(RULES
    rec[flip_0][1](E()) -> E()
    rec[flip_0][1](Z(x1)) -> O(rec[flip_0][1](x1))
    rec[flip_0][1](O(x1)) -> Z(rec[flip_0][1](x1))
    main(x1) -> rec[flip_0][1](x1))