With no explanation, label each line with "O", "event-attack/battle/war/militaryconflict", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport" or "building-hospital" preceded by ":".
During
the
American
Civil
War
it
was
used
as
a
Union
prison
camp
.
During:O
the:O
American:event-attack/battle/war/militaryconflict
Civil:event-attack/battle/war/militaryconflict
War:event-attack/battle/war/militaryconflict
it:O
was:O
used:O
as:O
a:O
Union:O
prison:O
camp:O
.:O