With no explanation, label each line with "O", "event-sportsevent", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
It
was
race
7
of
7
in
the
1950
World
Championship
of
Drivers
.
It:O
was:O
race:O
7:O
of:O
7:O
in:O
the:O
1950:O
World:event-sportsevent
Championship:event-sportsevent
of:event-sportsevent
Drivers:event-sportsevent
.:O