Spinning Rings - Fidget Spinner Edition

• Time : $O(1)$
• Space : $O(1)$

typedef unsigned long long ull;

ull spinningRings(ull innerMax, ull outerMax) {
    ull n = innerMax + 1, m = outerMax + 1;
    if (m < n) {
        ull r = n % m;
        if (m % 2 == r % 2) return n - m + (m - r) / 2;
        if (r % 2 == 0) return n - r / 2;
        return 2 * n - (m + (2 * r + 1) % m - 1) / 2;
    }
    if (n % 2 == 0) return n / 2;
    ull r = m % n;
    if (r == 0) return m;
    if (r % 2 == 1) return m + (n - r) / 2;
    return m + n - r / 2;
}