0 -> y
y -> x1
x1 -> y
y -> 0
z0 -> z1
z1 -> z0
x -> x1
x1 -> x
z1 -> z2
z2 -> z1
0 -> w0
w0 -> w1
w1 -> w0
0 -> u
0 -> i
i + x -> ix
ix -> i + x
ix -> ixp
ixp -> ix
u -> 0
i -> 0
ixp -> x
w0 -> 0
w1 -> 0
z0 -> 0
z1 -> 0
z2 -> 0
0 -> z2
0 -> z0
x -> 0