With no explanation, label each line with "O", "event-attack/battle/war/militaryconflict", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
At
the
zenith
of
prosperity
of
the
empire
,
the
An
Lushan
Rebellion
from
755
to
763
was
a
watershed
event
that
devastated
the
population
and
drastically
weakened
the
central
imperial
government
.
At:O
the:O
zenith:O
of:O
prosperity:O
of:O
the:O
empire:O
,:O
the:O
An:event-attack/battle/war/militaryconflict
Lushan:event-attack/battle/war/militaryconflict
Rebellion:event-attack/battle/war/militaryconflict
from:O
755:O
to:O
763:O
was:O
a:O
watershed:O
event:O
that:O
devastated:O
the:O
population:O
and:O
drastically:O
weakened:O
the:O
central:O
imperial:O
government:O
.:O