<s>
nodes	O
according	O
to	O
their	O
tree	B-Application
structure	O
.	O
</s>
<s>
Formally	O
,	O
this	O
operation	O
is	O
a	O
catamorphism	B-Application
.	O
</s>
<s>
Construct	O
a	O
tree	B-Application
with	O
the	O
root	B-Application
node	I-Application
as	O
the	O
entire	O
nation	O
and	O
each	O
level	O
representing	O
refined	O
geographical	O
areas	O
such	O
as	O
states/provinces	O
,	O
counties/parishes	O
,	O
cities/townships	O
,	O
and	O
polling	O
districts	O
as	O
the	O
leaves	O
.	O
</s>
<s>
formally	O
define	O
binary	O
tree	B-Data_Structure
accumulation	I-Data_Structure
as	O
iterative	O
application	O
of	O
a	O
ternary	O
operator	O
;	O
where	O
A	O
are	O
descendant	O
labels	O
and	O
B	O
is	O
a	O
junction	O
label	O
.	O
</s>
