With no explanation, label each line with "location-GPE", "O", "event-attack/battle/war/militaryconflict", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart" or "building-airport" preceded by ":".
During
the
period
when
the
Korean
War
occurred
,
Korea
divided
into
North
and
South
.
During:O
the:O
period:O
when:O
the:O
Korean:event-attack/battle/war/militaryconflict
War:event-attack/battle/war/militaryconflict
occurred:O
,:O
Korea:location-GPE
divided:O
into:O
North:O
and:O
South:O
.:O