#include <bits/stdc++.h>
using namespace std;

struct iofast_t {
    iofast_t() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} iofast;

struct uns_t {} uns;
template <typename Element, typename Head, typename ...Args>
auto vec(Element init, Head arg, Args ...args) {
    if constexpr (sizeof...(Args) == 0) return std::vector(arg, init);
    else return std::vector(arg, vec(init, args...));
}
template <typename Element, typename Head, typename ...Args>
auto vec(uns_t, Head arg, Args ...args) {
    return vec(Element(), arg, args...);
}

template <typename T, typename Compare = less<T>>
T &chmin(T &l, T r, Compare &&f = less<T>()) { return l = min(l, r, f); }
template <typename T, typename Compare = less<T>>
T &chmax(T &l, T r, Compare &&f = less<T>()) { return l = max(l, r, f); }

#include <atcoder/modint>
using mint = atcoder::modint998244353;

int main() {
    int64_t n, m; cin >> n >> m;

    if (n == 1) {
        cout << 0 << endl;
        return 0;
    }

    auto leq = vec<mint>(uns, m + 1);
    for (int i = 0; i <= m; ++i) {
        leq[i] = mint(i).pow(n - 1) * (mint(i) * (i + 1) / 2) * n;
    }

    auto geq = vec<mint>(uns, m + 2);
    for (int i = 0; i <= m + 1; ++i) {
        geq[i] = mint(m - i + 1).pow(n - 1) * (mint(m) * (m + 1) / 2 - mint(i) * (i - 1) / 2) * n;
    }

    mint ans = 0;
    for (int i = 1; i <= m; ++i) {
        ans += i * (leq[i] - leq[i - 1]);
        ans -= i * (geq[i] - geq[i + 1]);
    }

    cout << ans.val() << endl;
}