With no explanation, label each line with "location-GPE", "O", "event-sportsevent", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart" or "building-airport" preceded by ":".
Every
year
in
October
the
Porto
Marathon
is
held
through
the
streets
of
the
old
city
of
Porto
.
Every:O
year:O
in:O
October:O
the:O
Porto:event-sportsevent
Marathon:event-sportsevent
is:O
held:O
through:O
the:O
streets:O
of:O
the:O
old:O
city:O
of:O
Porto:location-GPE
.:O