#include <algorithm>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <tuple>
#include <vector>

#define mkp make_pair
#define mkt make_tuple
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define all(v) v.begin(), v.end()
using namespace std;
typedef long long ll;
// const ll MOD = 1e9 + 7;
const ll MOD = 998244353;
template <class T>
void chmin(T &a, const T &b) {
    if (a > b) a = b;
}
template <class T>
void chmax(T &a, const T &b) {
    if (a < b) a = b;
}

ll mod_pow(ll x, ll n) {
    x %= MOD;
    ll res = 1;
    while (n > 0) {
        if (n & 1) res = res * x % MOD;
        x = x * x % MOD;
        n >>= 1;
    }
    return res;
}

ll mod_inverse(ll x) {
    return mod_pow(x, MOD - 2);
}

void add(ll &a, ll b) {
    a = (a + b) % MOD;
}

void mul(ll &a, ll b) {
    a %= MOD;
    b %= MOD;
    a = a * b % MOD;
}

void solve() {
    ll N, M;
    cin >> N >> M;

    ll ans = 0;
    {  // max
        ll pre_value = 1;
        mul(pre_value, N);
        add(ans, pre_value);
        for (ll k = 2; k <= M; k++) {
            ll nex_value = 1;
            ll base = k * (k + 1) / 2;
            base %= MOD;
            mul(nex_value, base);
            mul(nex_value, N);
            mul(nex_value, mod_pow(k, (N - 1) % (MOD - 1)));

            ll res = nex_value;
            add(res, MOD - pre_value);
            mul(res, k);
            add(ans, res);
            pre_value = nex_value;
        }
    }

    {  // min
        ll pre_value = 1;
        mul(pre_value, N % MOD * M % MOD);
        add(ans, MOD - pre_value * M % MOD);
        for (ll k = M - 1; k >= 1; k--) {
            ll nex_value = 1;
            ll base = (M - k + 1) * (k + M) / 2;
            base %= MOD;
            mul(nex_value, base);
            mul(nex_value, N);
            mul(nex_value, mod_pow(M - k + 1, (N - 1) % (MOD - 1)));

            ll res = nex_value;
            add(res, MOD - pre_value);
            mul(res, k);
            add(ans, MOD - res);
            pre_value = nex_value;
        }
    }

    cout << ans << endl;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    solve();

    return 0;
}