With no explanation, label each line with "O", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport", "building-hospital" or "building-hotel" preceded by ":".
By
21:00
this
combined
force
had
managed
to
extract
the
1/9th
troops
.
By:O
21:00:O
this:O
combined:O
force:O
had:O
managed:O
to:O
extract:O
the:O
1/9th:O
troops:O
.:O