With no explanation, label each line with "location-GPE", "O", "other-medical", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart" or "building-airport" preceded by ":".
The
main
suppliers
of
heroin
to
the
US
have
been
Mexican
transnational
criminal
organizations
.
The:O
main:O
suppliers:O
of:O
heroin:other-medical
to:O
the:O
US:location-GPE
have:O
been:O
Mexican:location-GPE
transnational:O
criminal:O
organizations:O
.:O