0 QTRS
min(x, 0) → 0 min(0, y) → 0 min(s(x), s(y)) → s(min(x, y)) max(x, 0) → x max(0, y) → y max(s(x), s(y)) → s(max(x, y)) -(x, 0) → x -(s(x), s(y)) → -(x, y) gcd(s(x), s(y)) → gcd(-(s(max(x, y)), s(min(x, y))), s(min(x, y)))