⊦ ∃ i. i = 0 ∨ i + i + 1 = 0
Used simplifier rules: zero-07: ⊦ i + i = 0 ↔ i = 0;%add-a: ⊦ i + j + i0 = (i + j) + i0;%add-c: ⊦ i + j = j + i;