<snippet>
    <content><![CDATA[
constexpr int mod = 998244353;
namespace math {

    template<typename T>
    T gcd(std::initializer_list<T> args) {
        T res = 0;
        for (auto b : args) {
            for (T tmp; b != 0; ) {
                tmp = res % b, res = b, b = tmp;
            }
        }
        return res;
    }

    template<typename T>
    T lcm(std::initializer_list<T> args) {
        T res = 1;
        for (auto b : args) {
            if (!b) {
                return (T)0;
            }
            T g = std::gcd(res, b);
            res = (res / g) * (res / g) * g;
        }
        return res;
    }

    template<typename T>
    std::array<T, 3> exgcd(T a, T b) {
        if (b == 0) {
            return {a, 1, 0};
        }
        std::array<T, 3> r = exgcd(b, a % b);
        return {r[0], r[2], r[1] - a / b * r[2]};
    }

    template<typename T>
    T power(T a, T b, T m = mod) {
        T res = 1;
        for (a %= m; b > 0; b >>= 1, (a *= a) %= m) {
            if (b & 1) {
                (res *= a) %= m;
            }
        }
        return res;
    }
}
]]></content>
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</snippet>