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 ":".
Helicopters
may
be
fitted
with
tanks
(
helitankers
)
or
they
may
carry
buckets
.
Helicopters:O
may:O
be:O
fitted:O
with:O
tanks:O
(:O
helitankers:O
):O
or:O
they:O
may:O
carry:O
buckets:O
.:O