GEB

Σ = { M, I, U }

Ω₀ = MI
Ω? = MU

xI     → xIU
Mx     → Mxx
xIIIy  → xUy
xUUy   → xy

I(Ω₀) = 1
I(MU) = 0

I(xI → xIU)      = I
I(Mx → Mxx)      = 2I
I(xIIIy → xUy)   = I - 3
I(xUUy → xy)     = I

1 × 2ⁿ mod 3 ∈ {1, 2}
0 mod 3 ∉ {1, 2}

MI ⇏ MU