With no explanation, label each line with "product-airplane", "O", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
This
is
a
list
of
operators
of
the
Douglas
DC-4
,
Douglas
C-54
,
Canadair
North
Star
and
Douglas
R5D
.
This:O
is:O
a:O
list:O
of:O
operators:O
of:O
the:O
Douglas:product-airplane
DC-4:product-airplane
,:O
Douglas:product-airplane
C-54:product-airplane
,:O
Canadair:product-airplane
North:product-airplane
Star:product-airplane
and:O
Douglas:product-airplane
R5D:product-airplane
.:O