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 ":".
It
is
the
area
's
most
significant
collection
of
native
limestone
buildings
.
It:O
is:O
the:O
area:O
's:O
most:O
significant:O
collection:O
of:O
native:O
limestone:O
buildings:O
.:O