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 ":".
During
wartime
and
other
emergencies
,
rail
tracks
on
bridges
are
sometimes
paved
to
allow
road
traffic
to
proceed
.
During:O
wartime:O
and:O
other:O
emergencies:O
,:O
rail:O
tracks:O
on:O
bridges:O
are:O
sometimes:O
paved:O
to:O
allow:O
road:O
traffic:O
to:O
proceed:O
.:O