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 ":".
Sunscreens
were
installed
on
curves
directly
exposed
to
the
sunlight
to
keep
the
track
smooth
and
prevent
melting
.
Sunscreens:O
were:O
installed:O
on:O
curves:O
directly:O
exposed:O
to:O
the:O
sunlight:O
to:O
keep:O
the:O
track:O
smooth:O
and:O
prevent:O
melting:O
.:O