| i0 < 0, i < 0 ⊦ gcd(abs(i), abs(i0 + i)) = gcd(i, i0), i = 0, i0 = 0, 0 < i ∧ i < i0 + i |
⊦ 0 < i ∧ i < j → gcd(i, j) = gcd(i, j - i)
i < 0, i0 < 0 ⊦ gcd(abs(i), abs(i0 + i)) = gcd(i, i0), i = 0, i0 = 0, 0 < i ∧ i < i0 + i, 0 < abs(i) ∧ abs(i) < abs(i0 + i)
i < 0, i0 < 0, 0 < abs(i), abs(i) < abs(i0 + i) ⊦ gcd(abs(i), abs(i0 + i) - abs(i)) = gcd(i, i0), i = 0, i0 = 0, 0 < i ∧ i < i0 + i
Used terms: abs(i0 + i), abs(i)