o = next_marker(seq, ["<output>"], start=k + 1)
e = next_marker(seq, ["<input>", "<prog>"], start=o)
if o is None or e is None:
o = next_marker(seq, ["<output>"], start=k + 1)
e = next_marker(seq, ["<input>", "<prog>"], start=o)
if o is None or e is None: