⊦ ∃ i0. i0 + i0 = i + i ∨ 2 + i0 + i0 = i + i + 1
Used simplifier rules: add-in: ⊦ i + j = i + i0 ↔ j = i0;%add-a: ⊦ i + j + i0 = (i + j) + i0;%add-c: ⊦ i + j = j + i;