With no explanation, label each line with "location-GPE", "O", "person-politician", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart" or "building-airport" preceded by ":".
Ivan
Asen
and
the
Emperor
of
Nicaea
,
John
III
Vatatzes
,
concluded
an
alliance
against
the
Latin
Empire
at
their
meeting
in
1235
.
Ivan:O
Asen:O
and:O
the:O
Emperor:O
of:O
Nicaea:location-GPE
,:O
John:person-politician
III:person-politician
Vatatzes:person-politician
,:O
concluded:O
an:O
alliance:O
against:O
the:O
Latin:O
Empire:O
at:O
their:O
meeting:O
in:O
1235:O
.:O