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 ":".
The
first
flight
of
the
prototype
took
place
in
September
1988
and
a
contract
was
signed
for
29
upgraded
aircraft
in
December
of
that
year
.
The:O
first:O
flight:O
of:O
the:O
prototype:O
took:O
place:O
in:O
September:O
1988:O
and:O
a:O
contract:O
was:O
signed:O
for:O
29:O
upgraded:O
aircraft:O
in:O
December:O
of:O
that:O
year:O
.:O