7
EVEN
Ï
MSO
•
Proposition
EVEN is not expressible in MSO
•
•
Proof
:
•
Will show that if
s
=
;
and
|A|, |B|
¸
2
k
then duplicator has a winning strategy in k
moves.
•
We only need to show how the duplicator
replies to set moves by the spoiler [why ?]