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 ":".
Of
2,000
glaciers
observed
,
99
%
are
retreating
.
''
Of:O
2,000:O
glaciers:O
observed:O
,:O
99:O
%:O
are:O
retreating:O
.:O
'':O