#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
#define pb push_back
#define all(a) a.begin(), a.end()
#define sz(a) ((int)a.size())
const int mod = 998244353, N = 1 << 21, G = 3;

ll add(ll a, ll b) {
    a += b;
    if (a >= mod) {
        a -= mod;
    }
    return a;
}

ll sub(ll a, ll b) {
    a -= b;
    if (a < 0) {
        a += mod;
    }
    return a;
}

ll mul(ll a, ll b) {
    return a * b % mod;
}

ll mpow(ll a, ll b) {
    ll ans = 1;
    for (; b; b >>= 1, a = mul(a, a)) {
        if (b & 1) {
            ans = mul(ans, a);
        }
    }
    return ans;
}

struct NTT {
    ll w[N];
    NTT() {
        ll dw = mpow(G, (mod - 1) / N);
        w[0] = 1;
        for (int i = 1; i < N; ++i) {
            w[i] = mul(w[i - 1], dw);
        }
    }
    void operator () (vector <ll> &a, bool inv = false) {
        int x = 0, n = a.size();
        for (int j = 1; j < n - 1; ++j) {
            for (int k = n >> 1; (x ^= k) < k; k >>= 1);
            if (j < x) {
                swap(a[x], a[j]);
            }
        }
        for (int L = 2; L <= n; L <<= 1) {
            int dx = N / L, dl = L >> 1;
            for (int i = 0; i < n; i += L) {
                for (int j = i, x = 0; j < i + dl; ++j, x += dx) {
                    ll tmp = mul(a[j + dl], w[x]);
                    a[j + dl] = sub(a[j], tmp);
                    a[j] = add(a[j], tmp);
                }
            }
        }
        if (inv) {
            reverse(1 + all(a));
            ll invn = mpow(n, mod - 2);
            for (int i = 0; i < n; ++i) a[i] = mul(a[i], invn);
        }
    }
} ntt;

ll fac[N], facp[N];

int main() {
    ios::sync_with_stdio(false), cin.tie(0);
    fac[0] = facp[0] = 1;
    for (int i = 1; i < N; ++i) {
        fac[i] = mul(fac[i - 1], i);
        facp[i] = mpow(fac[i], mod - 2);
    }
    int n, m;
    cin >> n >> m;
    vector <ll> a(N);
    for (int i = 0; i <= m; ++i) {
        a[i] = fac[m] * facp[i] % mod * facp[m - i] % mod * facp[m - i] % mod;
    }
    ntt(a);
    for (int i = 0; i < N; ++i) {
        a[i] = mpow(a[i], n);
    }
    ntt(a, true);
    ll res = 0;
    for (int i = 0; i <= n * m; ++i) {
        if (i & 1) {
            res = sub(res, mul(a[i], fac[n * m - i]));
        } else {
            res = add(res, mul(a[i], fac[n * m - i]));
        }
    }
    res = mul(res, mpow(fac[m], n));
    cout << res << '\n';
}