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 ":".
They
were
mainly
used
by
second
line
units
.
They:O
were:O
mainly:O
used:O
by:O
second:O
line:O
units:O
.:O