With no explanation, label each line with "location-GPE", "O", "product-weapon", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart" or "building-airport" preceded by ":".
The
extreme
weight
of
the
``
Ferdinand
``
made
towing
difficult
:
the
standard
armored
recovery
vehicle
in
German
service
at
the
time
was
the
``
Bergepanzer
IV
``
,
a
variant
of
the
``
Panzer
IV
``
that
could
tow
a
single
``
Panzer
''
IV
without
assistance
.
The:O
extreme:O
weight:O
of:O
the:O
``:O
Ferdinand:product-weapon
``:O
made:O
towing:O
difficult:O
::O
the:O
standard:O
armored:O
recovery:O
vehicle:O
in:O
German:location-GPE
service:O
at:O
the:O
time:O
was:O
the:O
``:O
Bergepanzer:product-weapon
IV:product-weapon
``:O
,:O
a:O
variant:O
of:O
the:O
``:product-weapon
Panzer:product-weapon
IV:product-weapon
``:O
that:O
could:O
tow:O
a:O
single:O
``:product-weapon
Panzer:product-weapon
'':product-weapon
IV:product-weapon
without:O
assistance:O
.:O