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 ":".
Only
one
crew
member
is
at
work
at
a
time
:
this
person
takes
an
empty
train
to
the
coal
load
out
,
then
changes
to
the
loaded
train
to
take
it
back
to
the
power
plant
.
Only:O
one:O
crew:O
member:O
is:O
at:O
work:O
at:O
a:O
time:O
::O
this:O
person:O
takes:O
an:O
empty:O
train:O
to:O
the:O
coal:O
load:O
out:O
,:O
then:O
changes:O
to:O
the:O
loaded:O
train:O
to:O
take:O
it:O
back:O
to:O
the:O
power:O
plant:O
.:O