With no explanation, label each line with "O", "event-other", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
``
Many
months
after
it
happened
,
the
Bolshevik
revolution
was
still
a
very
hazy
and
contradictory
phenomenon
.
``:O
Many:O
months:O
after:O
it:O
happened:O
,:O
the:O
Bolshevik:event-other
revolution:event-other
was:O
still:O
a:O
very:O
hazy:O
and:O
contradictory:O
phenomenon:O
.:O