Input TRS:
    1: sel(|0|(),cons()) -> X
    2: sel(s(),cons()) -> sel(X,Z)
    3: dbl(|0|()) -> |0|()
    4: dbl(s()) -> s()
    5: dbls(nil()) -> nil()
    6: dbls(cons()) -> cons()
    7: indx(nil()) -> nil()
    8: indx(cons()) -> cons()
    9: from() -> cons()
Extra variable in rule 2.
NO