Proof of Lemma 2 (end)

m delivered (to p)

0-valent

m delivered

0-valent

1-valent

0-valent

We stick the delivery of m after each step (look at Case 1)

There has to be

a step which before

it we have 0-valent

and after 1-valent.

This step has to be

made by p.

This is a decider!