<s>
Extremal	B-Algorithm
combinatorics	I-Algorithm
is	O
a	O
field	O
of	O
combinatorics	O
,	O
which	O
is	O
itself	O
a	O
part	O
of	O
mathematics	O
.	O
</s>
<s>
Extremal	B-Algorithm
combinatorics	I-Algorithm
studies	O
how	O
large	O
or	O
how	O
small	O
a	O
collection	O
of	O
finite	O
objects	O
(	O
numbers	O
,	O
graphs	O
,	O
vectors	O
,	O
sets	O
,	O
etc	O
.	O
)	O
</s>
<s>
Much	O
of	O
extremal	B-Algorithm
combinatorics	I-Algorithm
concerns	O
classes	O
of	O
sets	O
;	O
this	O
is	O
called	O
extremal	B-Algorithm
set	I-Algorithm
theory	I-Algorithm
.	O
</s>
<s>
The	O
latter	O
question	O
is	O
answered	O
by	O
Sperner	O
's	O
theorem	O
,	O
which	O
gave	O
rise	O
to	O
much	O
of	O
extremal	B-Algorithm
set	I-Algorithm
theory	I-Algorithm
.	O
</s>
