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
an
ancient
medieval
borough
characterized
by
the
majestic
walls
of
a
fortress
.
It:O
is:O
an:O
ancient:O
medieval:O
borough:O
characterized:O
by:O
the:O
majestic:O
walls:O
of:O
a:O
fortress:O
.:O