[ Anai's Problem ]
(s,z)
2
[
[s z  + s - 1 >= 0 /\ s = 0 /\  z  + 1 >= 0]
\/ [s z  + s >= 0 /\ s = 0 /\  z  = 0] \/
[s^2  + 4 s z  >= 0 /\ [[
s^2  - 2 s <= 0 /\ s z  + s - 1 <= 0 /\ s = 0 /\ [
s^2  + 3 s z  - s - 2 z  <= 0
 \/ [s +  z  - 1 <= 0 /\ [s z  + s - 1 = 0 \/
z  = 0]]] /\ [s + 2 z  >= 0 \/  z  = 0]] \/
[s^2  - 2 s <= 0 /\ s + 2 z  >= 0 /\ s = 0 /\ [
[s^2  + 3 s z  - s - 2 z  <= 0 /\ [s z  + s - 1 <= 0
\/ z  = 0]] \/ [s +  z  - 1 >= 0 /\
[s z  + s - 1 >= 0 \/  z  = 0]]]]]] \/
[s = 0 /\  z  >= 0]
].
finish
