⊦ ¬ i < j → (i ≠ j ↔ j < i)
¬ ¬ gcd(i, j) < gcd(abs(i), abs(j)) ⊦ gcd(i, j) = gcd(abs(i), abs(j))
¬ gcd(i, j) < gcd(abs(i), abs(j)) ⊦ ¬ gcd(abs(i), abs(j)) < gcd(i, j)
Used terms: gcd(abs(i), abs(j)), gcd(i, j)