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 ":".
57
swimmers
were
entered
in
the
event
,
of
which
55
swam
.
57:O
swimmers:O
were:O
entered:O
in:O
the:O
event:O
,:O
of:O
which:O
55:O
swam:O
.:O