With no explanation, label each line with "location-GPE", "O", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
It
then
flew
back
to
London
in
the
afternoon
.
It:O
then:O
flew:O
back:O
to:O
London:location-GPE
in:O
the:O
afternoon:O
.:O