With no explanation, label each line with "O", "other-chemicalthing", "other-medical", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart" or "building-airport" preceded by ":".
The
difference
between
the
vardenafil
molecule
and
sildenafil
citrate
is
a
nitrogen
atom
's
position
and
the
change
of
sildenafil
's
piperazine
ring
methyl
group
to
an
ethyl
group
.
The:O
difference:O
between:O
the:O
vardenafil:other-medical
molecule:other-medical
and:O
sildenafil:other-medical
citrate:other-medical
is:O
a:O
nitrogen:other-chemicalthing
atom:other-chemicalthing
's:O
position:O
and:O
the:O
change:O
of:O
sildenafil:other-medical
's:O
piperazine:other-medical
ring:other-medical
methyl:other-medical
group:other-medical
to:O
an:O
ethyl:other-medical
group:other-medical
.:O