#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;

vector <ll> Mul(vector <ll> a, vector <ll> b, int bound = N) {
    int m = a.size() + b.size() - 1, n = 1;
    while (n < m) n <<= 1;
    a.resize(n), b.resize(n);
    ntt(a), ntt(b);
    vector <ll> out(n);
    for (int i = 0; i < n; ++i) out[i] = mul(a[i], b[i]);
    ntt(out, true), out.resize(min(m, bound));
    return out;
}

// vector <ll> Ln(vector <ll> a) {
//     int n = a.size();
//     if (n == 1) return {0};
//     vector <ll> d
// }

// vector <ll> Pow(vector <ll> a, ll k) {
//     int n = a.size(), m = 0;
//     vector <ll> ans(n, 0);
//     while (m < n && a[m] == 0) m++;
//     if (k && m && (k >= n || k * m >= n)) return ans;
//     if (m == n) return ans[0] = 1, ans;
//     ll lead = m * k;
//     vector <ll> b(a.begin() + m, a.end());
//     ll base = mpow(b[0], k), inv = mpow(b[0], mod - 2);
//     for (int i = 0; i < n - m; ++i) {
//         b[i] = mul(b[i], inv);
//     }
//     b = Ln(b);
//     for (int i = 0; i < n - m; ++i) {
//         b[i] = mul(b[i], k % mod);
//     }
//     b = Exp(b);
//     for (int i = lead; i < n; ++i) {
//         ans[i] = mul(b[i - lead], base);
//     }
//     return ans;
// }

vector <ll> mmpow(vector <ll> a, ll k) {
    if (k == 1) {
        return a;
    } else {
        vector <ll> res = mmpow(a, k / 2);
        res = Mul(res, res);
        if (k & 1) {
            res = Mul(res, a);
        }
        return res;
    }
}

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(m + 1);
    for (int i = 0; i <= m; ++i) {
        a[i] = fac[m] * facp[i] % mod * facp[m - i] % mod * facp[m - i] % mod;
    }
    vector <ll> ans = mmpow(a, n);
    ll res = 0;
    for (int i = 0; i <= n * m; ++i) {
        if (i & 1) {
            res = sub(res, mul(ans[i], fac[n * m - i]));
        } else {
            res = add(res, mul(ans[i], fac[n * m - i]));
        }
    }
    res = mul(res, mpow(fac[m], n));
    cout << res << '\n';
}