With no explanation, label each line with "O", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport", "building-hospital" or "building-hotel" preceded by ":".
Experts
of
the
time
believed
the
project
to
be
infeasible
due
to
the
difficult
terrain
.
Experts:O
of:O
the:O
time:O
believed:O
the:O
project:O
to:O
be:O
infeasible:O
due:O
to:O
the:O
difficult:O
terrain:O
.:O