$ENTRY Go {
    , ((1) 2 ((3 4) 5) ((())) (((6))) 7 8 ()): e.List
    = <Prout e.List ' -> ' <Flatten e.List>>
};

Flatten {
    = ;
    s.I e.X = s.I <Flatten e.X>;
    (e.X) e.Y = <Flatten e.X> <Flatten e.Y>;
};